[exterminator20]

another thing to check is That setting, the advanced network functionality unchecked, should remain unchecked. Once you disable the advanced network functionality the first time, you do not have to go there anymore.
Just a side note, If you have changed the the ROMs like you said then it probably did not re-enable that option. you have to go back and disable it.

*there is also a chance that from trying to connect unsuccessfully there may be some of the following processes still running which will also prevent a connection and are responsible for error message "you might need active sync 4.5 or higher"
in this case, just kill "rapimgr.exe", "WCESMGR.exe" and "wcescomm.exe" in taskmgr; then clear port 990 in whatever program is using it, restart Microsoft Activesync and try again