It may not be your router. Routers are likely to fail altogether, rather then work interminently.
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Your best bet is to first borrow a known router to check your connection.
Not true at all! In fact my experience is that routers tend to fail in a piece-meal fashion and rarely fail totally all at once - unless struck by lighting!
I had a Netgear DG834G that started to regularly drop the internet connection needing frequent re-boots. I replaced the power supply which fixed the problem.
I replaced that with a DG834GT in order to run the DG Team customised firmware. The modem and router parts work fine, but the wireless would drop out randomly. I replaced the wireless function with a separate Buffalo access point that is much more reliable and all is now hunky dory.
I am now thinking of getting an "N" class access point to replace the Buffalo as I am still happy with the Netgear's modem and router functions.
Demon dial-up ('97) > Freeserve dial-up ('00) > Zen 512 ('02) > Metronet PayGo 1000 ('04) > Newnet Home 2050 Lite ('05) > Home 8050 Lite ('06) > Home 8050 M ('07) > back down to Home 8050 Lite ('07) > Be Value > ('08) > O2 Standard ('09) > Orange Broadband and Anytime Calls ('10) > ?