Have a new (refurb) Curve 8310 with AT&T, WinXP Pro, v4.3 Desktop and suddenly started getting "Unknown Error Reported" during intellisync and my Curve would not sync with my PC.
Did a bunch of searching, installing/reinstalling software, thought perhaps it could be because of the changes I made deleting .cods per John Clark's thread, though that didn't make any sense b/c my BB has been fine for a couple days now.
Anyhow, what fixed it is uninstalling both the OS & DM from my PC, manually deleting all "Research In Motion" folders/files, then reinstalling both and it works again.
Never had this problem with my 8700 & older version of DM, I sure hope this doesn't keep happening - big, big pain in the rear and very big waste of time.
Just thought I'd share my resolution with you guys.