Hi David,
I can only guess at this since I don't do many project transfers these days, and never to MySQL.
Regardless of what I have to say, check this thread often, or set a notification on the thread, since another user may be able to solve the problem or provide a workaround.
My immediate suspicion is that a version change of some product is causing the difficulty. The first thing to check is whether you have recently updated your EA build. If so, and you are not yet at the current build (834) then update again in case the problem has been addressed there. If not...
Perhaps you have updated your MySQL build. Check both the DBMS engine and your client software, since either could affect things. Regardless of whether you have made a recent change, obtain the version and build (whatever the equivalent term is for MySQL) numbers. You also want to capture the actual software application names for both, since there are multiple data engines and drivers for MySQL.
Once you have all the software information, send a bug report to Sparx immediately. If you are a registered user, then use the bug report link on the Registered Users page. This will let you attach a file, so perhaps you can attach a sample project where this happens. Make sure to provide the complete configuration information you captured above.
My guess - yes, this is another one, but it is a good bet - is that the Sparxians are hunkering down to work on EA 7.5, which should go into beta testing in a few more builds. There might not be another production build released before then (or perhaps only a single one). You need to get your bug report in now so it gets into the hopper before beta testing issues flood the queue.
Please let us know what happens.
David