Network unstable. I get this quite often. Lately it happens more frequently in the afternoon through 10:30 at night. I hooked a network monitor up and I see resets and null or zero len packets. I have isolated all I can and bypassed the router, replaced cable, Replaced NIC, and made sure that there was no electrical interference close to the cat 5 cable. There are times it gets so bad I can do nothing. The same exact thing shows on both NICs so I am sure it is not a hardware issue in my PC.