One would be to update flash, but are you running FM Pro on server?
This happened on 3 different machines in the last couple days.
All running FM12 with remote data on a server
I'm guessing this is on windows, can you view the same contents in IE to see if you get a more verbose error?
i have been getting this error on several different websites over the past few days. Updating the flash player seems to have resolved it, at least for the time being.