It almost looks as if you have a partial 1.51 installation of DBI on your machine as well! My understanding is that when Dynaloader is called by DBI's initialisation code it will attempt to load the matching compiled code. But in this case Dynaloader appears to be saying that it is seeing a 1.51 version compiled code and a 1.50 object.

The latest version of both DBI and DBD-mysql are available from the usual PPM repositories and it might be as well to just update to the very latest and you troubles should go away. HOPEFULLY!

jdtoronto