Modem restarts while connected to router

Hello everyone !

I recently got time warner cable and it has caused me a lot of headache. I have a Ambit u10c018 modem and I connect it to my Dlink DI-524 router to access internet using my laptop. From last 2 months, the internet keeps dropping every now and then. pages stop loading suddenly and I notice a yellow triangle over the internet signal icon in the bottom right corner. the "send" light in the router goes off during the disconnected time and ready light keeps blinking (rest light remains as they remain while internet working). then if i restart the modem everything gets ok. I tried hooking up the modem directly to my PC, and then I dont get any disconnection problem.
I tried contacting TWC but their customer support is nothing but crap.. So, please help me in solving this problem..
(oh BTW, until recently I was using this router in my previous apartment with Cox Internet and I never got such problem..)