Downgrade completed and disconnected battery for 30 minutes. No change.
No media audio still.
It doesn't appear that I can go back to 3.00, is that correct?
You mean v3.x of the Nav software? Possibly. From what I understand, when you insert an update SD, the system checks the version number and only proceeds if the SD contains a newer version. Some have used Testmode "Force Write" load older software. I've never done that so I can't help.
And from another post I got the impression that you have already tried the simpler method to revert to the previous installation - by deleting or creating (as the case may be) the PRG.FLG file in USER.
But before you do anything, have you tried powering off and on your phone? Even removing the battery for a few minutes (if possible with your phone). I know this has solved the issue for some people (IIRC iPhones - but who knows?).
Otherwise, I'm about out of ideas. Sorry. It would be interesting to know if anyone else with your make/model phone is having issues. It sounds like you are running a custom ROM, so that may complicate things.