^^ Try to isolate the problem..Remove the router, connect modem directly to computer..

My experience with WRT54Gbeen using for 5yrs w/o major problems)
- firmware upgrade to fix bugs
- Poor ventilation causes overheating and stalls the device
- Adaptor is Transformer type(not auto volt), if commercial power sags, chances are youll get DC or causes router to hang.. Connect adaptor to line interactive UPS or better replace adaptor w/ switching type 12VDC 1A.
Also set modem lease time to max..You will get DC if lease time expires and reset would solve the problem temporarily. Ask isp to replace modem for isolation purposes.

Overall ok naman ang linksys though performance is not as good as hardened-carrier grade device. For small-office-home-office use lang talaga