Hey all, i have searched at xda and over here and it seems to be a known problem that many people cannot connect their devices to their computers after upgrading to SP3. the only thing i found was a thread posted by colisonne at xda. he showed my this quote and said it helped him.
"Yahoo. Re: ActiveSync 4.5 with Dell Axim x5. I had the same problem, and since it is a work computer and came with sp3 installed, I didn't have any rollback options. I got this pig to run, by adding the ports ActiveSync uses as exceptions under the firewall setting in control panel. We do not have windows firewall running on each computer, but manage our settings by the Group Policy approach. Either way, open the Control Panel, Windows Firewall, Exceptions tab. You should already see 4 activesync entries named ActiveSync Application, ActiveSync Connection Manager, ActiveSyncRAPI Manager and ActiveSync Service. The ActiveSync Service entry takes care of port 26675, so I added 5 additional ports. I named them ActiveSync 900, ActiveSync 990, ActiveSync 5721, ActiveSync 5678 and ActiveSync 5679 so I could identify the port numbers that they controlled and why they were added. Enter the numbers in the port block. I removed the ppc from the cradle and rebooted the pc. When I reinserted the ppc in the cradle, voila, the device was detected and I was then walked through the Partnership Setup. I still have to setup sync options, but at least they talk."
don't know if this is the right place to post it but i hope it helps someone who needs it (havent had time to try it myself)