I had one where my integrated nic was disconnecting me every 45 minutes or so during Malta way back. That was not fun. Turned out to be undervoltage on the motherboard and failing PSU causing this and other problems. Had to do with warm-up cycles or at least loss in efficiency (or progression of failure) as the PSU was running.
Also had full-screen lockups with stuttering sound and frozen picture. Had some other issues. The symptoms were scattered and really hard to track down. Didn't confirm anything for a long time until I went into my BIOS screen and saw the readouts for my voltage rails seriously lower than they should have been.
Swapped it out and whattayaknow, the symptoms stopped!
PSUs are very hard to spot as they fail, but if you've got a hunch check your voltage readouts. If you've got a PC that lets you monitor those from your OS, even better. Otherwise check your BIOS.
