Problems with voting are being reported in realtime on this map (the site is rather slow, I had to reload several times).
Ohio (!) is leading the pack at the moment, as this report from Columbus indicates:
Franklin County phone system returns to serviceThe Columbus DispatchTuesday, November 7, 2006 9:50 AM
Franklin County's phone system was returned to service about 90 minutes after it collapsed today under a crush of calls from voters and poll workers.
The volume of calls “overwhelmed the system,” Franklin County Elections Director Matthew Damschroder said.
Phones returned to normal about 9:30 a.m. The system also went down during the May 2 primary, delaying final returns until 2 a.m.