possibly related to the IE settings, especially the proxy server restore settings etc, see instruction below. it;s also worth trying reset the modem to factory defaults.

http://www.tp-link.com/en/article/?faqid=84

This problem happen on me everyday, after restarting itself, web configuration often cannot be accessed.
Then after it restarting next time, i can access web configuration again. Sometimes nothing happen to modem configuration access.

It restarts about 3 times /day.

Before I got same problem but less often. I'd already got the replace of this type few days ago, But same thing happen and the problem got more severe.

FYI my internet connection speed now is 5 Mbps

There are about 10 wireless client connecting to this modem now.
I'm also connecting this modem to TL-R470T+ (to manage about 3 switch - 20-30 connection from ethernet cable).
and one of switch at 3rd floor connected to TL-WR941ND wan port as access point.

Anyone know the reason for this thing happen?
My TP Link customer service said it because previously I've had 3 mbps connection the router overload and cannot share too many bandwidth to many devices.
Now my connection upgraded to 5 mbps and same thing still happen.

There is talk about changing the adapter to 12 V because there is possibility the modem lack of power to broadcast wireless signal (you can put fan in front of it).
But another people said I can damage the router for overheating and even burn this modem. if adaptor lack of power the device would not be able to work at first.

Do you think my modem cannot handle too many connection even after i place another router to manage cable user?
TP-link suggest this modem recommended max user number for this modem is 20.
That's why i bought TL-R470T+ to reduce workload of this modem, but seems it doesn't help anything at alll.

My conversation with TP-Link's CS

harrison.li@tp-link.com

Dec 23 (4 days ago)

Reply
to me

Sorry sir, for 8961 was added with new security mechanism, one can't relogin if leave the management interface for long time. However, it doesn't affect the modem's function at all. We have to reboot the modem if you want to access the modem after leaving for long.

Sorry for the inconvenience again.
Any further help, please feel free to contact me.
Kim

Dec 23 (4 days ago)

to Harrison.li
Is it not because it lack of ampere?
other people said to try changing adapter from 0,85 to 1 A.

My modem also would be restarting few times a day if there are 10
wireless device connected through it.
harrison.li@tp-link.com

Dec 23 (4 days ago)

Reply
to me

Dear sir

High power can improve the situation temporarily, but may be harmful to the modem, which is beyond our guarantee for the product. So the adapter had better be consisted with the modem, it's better to use the original one in the packet.
We advice less than 8 devices connect at the same time as the more devices there are , the rom of the modem will be more occupied, the worse wireless environment you may suffer. Then you may suffer from Internet dropping or modem dropping. Hope your understanding.

If you need more help, please feel free to contact me.

They explain to you that you have bought a router for 2-3 devices no more (is it a router ? lol) and they don't know nothing in electronics (1A adaptor may be harmful lol)... That's why products support is useless.

TP-link Indo's fb fanpage admin https://www.facebook.com/TPLINKIndonesia?filter=2
said to try changing my adapter to 1A but use same voltage to prevent damaging the board.

a lot of td-w8151n users have same problem like this and the solution is simple changing adapter from 0,6A to 0,85A, lol.
It seems this product lack of power as wireless router.
Crazy, they still dare to sell product with unsuitable adapter.

I have same problem. After I login to web page control, after some ours or minutes I can't enter to the web page control again.
I have make PING command to Modem IT is all right, But I cant Open the 192.168.1.1 web page on my browser.
I have try 2-3 computer and Mobile devices too. I need to turn off and turn on modem manualy, and after it began to work but for a while.
I have make even factory reset and change this Modem to new one. But the problem is still stay.
Waiting a best choice. Thank you. :)

I believe I have an answer. I turned off the wireless by using the button on the rear panel. Then, I turned the power off (using the power button) for about 15 minutes to let the modem cool down. After pressing the power button to on, I was able to login.

I have been using only an ethernet connection for a long time before I activated and started using wireless. Using wireless causes the modem to heat up.

I did not have to change anything else.

eclafikos wrote

I have same problem. After I login to web page control, after some ours or minutes I can't enter to the web page control again.
I have make PING command to Modem IT is all right, But I cant Open the 192.168.1.1 web page on my browser.
I have try 2-3 computer and Mobile devices too. I need to turn off and turn on modem manualy, and after it began to work but for a while.
I have make even factory reset and change this Modem to new one. But the problem is still stay.
Waiting a best choice. Thank you. :)

I have a TD-W8961ND too and suffer of exactly the same problem. I can't login to the web interface more than once after restarting the device. I recently updated the firmware hoping that would fix it but no, it didn't. Please, provide some support about this common issue.

TP-Link has a big problem with this issue. But not answers.

How many time is next firmware update ? As harrison.li@tp-link.com told us, change the charger is no a solutión, so, please fix the problem ASAP.

I have the same issue here and trying to figure out a solution...
Its a shame the attention we have getting back from TP-Link...
I am looking for an alternative firmware to it but no sucess! =/