sorry to hear you have problems.
What happened shortly prior to this problem, did you install some firmware?
Please use PRS+ installer to dump current firmware (it's somewhere in expert options). All partitions that are available. This might give us an idea of what's going on.
And, by the way, copying the file that gets md5 error back to /Data (internal memory) under a different name and comparing it to the right one would also help.