I tried to play around with a few partitions and formats etc in the Mac Disk Utility application, and now my Panasonic HMC70 will not recognize my memory card.

How can I wipe it and start from scratch?

I'll need very clear instructions as I am no computer whiz!

Does the camera have a "format" function? Should be one buried in the menus somewhere, just be sure you format the correct media if you have card and HD...

Not familiar with your cam offhand, but I think this will do the trick for you.

I formatted it back to MS Dos mode and it worked :)