I've found a workaround - sorry it's in German - here:
But it seems that since ActiveSync 4.5 you need to configure a DOMAIN on the pocketPC, not only login and password.
Does anybody know how to set something like a "pseudo domain" or if the PC has a "default domain", if no domain is set?
I will try to translate the workaround now:
In earlier versions of ActiveSync WLAN Sync was possible (last known version 3.8), since version 4.x it was removed..
You can do a remote WLAN Sync as followed:
Start ActiveSync on the PocketPC. Go to Options > Server OR Configure Server [depends on your ActiveSync Version]
Enter the IP of the Windows PC. [if you don't know do: Start > Run > cmd > ipconfig /all ]
Enter Login and Password which are the same as on your Windows PC. [SSL I think should be deactivated]
IN v4.5 YOU HAVE A PROBLEM HERE: if you don't enter a DOMAIN, the configuration wizard doesn't continue
IF YOU HAVE LOWER VERSION PLEASE TELL WHETHER YOU HAVE TO SPECIFY A DOMAIN
Click Next > Next > Finished.
Now you can MAYBE [see the DOMAIN problem] sync via WLAN again..
If anyone has an idea how to workaround the MUST-SPECIFY-A-DOMAIN problem please tell, I think I am not the only one who wants WLAN Sync back!