Solved. Winuae must be run as administrator, to mount Work on cf card.
All good now.
Huh, I assumed you wanted to mount the partition within the Amiga workbench while using real amiga.
I personally mount it and then use PCMCIA to transfer files to it. Else I just remove card and update Emu68 that way.
4GB is rather large for Emu68 partition though. They say not to make large partitions or fill them over half way. As it can cause problems.