Problems connecting to WinCE 5.0 device with ActiveSync 4.5

I develop on .NETCF on a WinXP pmachine.
Up to some days ago I used to connect to my WinCE 5.0 device with
ActiveSync 4.5 with my laptop without problems.
Now ActiveSync gives me following error and I cannot connect to the
device:
"Cannot verify the version of ActiveSync on your device. A program
such as a firewall may be blocking a port ActiveSync uses to connect
to the device, or you may need to upgrade to a more recent version of
ActiveSync on the PC."
I have disabled firewall, changed ports, changed usb cables,
reinstalled ActiveSync 4.5.... to no effect.
My desktop PC with XP can connect perfectly with ActiveSync 4.5 to the
same devices.
I am sure the device has not changed but it is possible that some
WinXp patches have got installed on the PC in the meantime.

I have seen on Inet some other peoples complaininga about this error,
the only solution being disinstalling some strange modems that I don't
have or killing and restarting the activesync thing.

Effectively, by doing the following steps I can successfuly connect
after a failure.
1) detach usb cable with the device
2) kill rapimgr.exe from task manager
3) restart C:\Programs\Microsoft ActiveSync\rapimgr.exe
4) attach usb cable to the device
I have no need to reset the device but if I restart my laptop the
problem returns and I have to redo all.
After a successfull connection I have the chance to compare the
success and fail communication log.

In particular the failures of the communucation are in the followings
log lines:
wcesmgr.log:
- 04/20/2011 10:47:34.203 Error 0x8000BADD: Failed to get version
number from device.

but BEFORE it ...
wcescomm.log:
- 04/20/2011 10:47:28.359 - CesProxy: Close Win socket 990
- 04/20/2011 10:47:28.359 - Connection: Init RAPI port failed
0x8007271D.

Some help on the causes of this rapi error? My 990 tcp port is open.
But it appears that the first time it is accessed wcescomm.exe gives
out an error.

Thanks.