As this seems to be the most active C128 thread (and because Redrumloa actually sells these things), I've noticed that a lot of people on other forums are having trouble getting their MMC64Replay cartridges to run *.T64 tape images using the v0.07 T64PLGIN plugin (it freezes when attempting run run an image). I managed to track down an earlier one v0.04 (BIN only) and it works fine!
Also, I had hell mounting D64 images as virtual drives when setting the defaults 12/13 and a real 1571 FDD attached as device 8. Once I hardware changed the 1571 to device 10 then the problem went away and virtual disks mounted fine.