I was recently having disconnect problems like the OP described. Did the usual: delete cache, removed OC's rebooted router and checked the network cabling. Went away for about a week then it returned. I did everything again with no changes. One would DC, log it in, another would dc, log it in and it would dc, then another would dc etc. All while standing still.

I was fed up and was going to plug my modem direct to the pc but when I yanked the router off the wall it was cooking. Cisco E-3000 with a dd-wrt firmware. Great routers that get warm but this was way too hot. Running an oscillating fan on the backside lowered the temp and this stopped all my dc's. I had run this router for over a year in this position without issue.

TLDR: Router overheat caused my DC's.