I recommend downloading Sk@leTracker (a win32 remake of the good old fasttracker 2 by Triton) and use it to load and resave the modules, then try them in Blitz again. It may just be the tracker you're using at the moment screwing something up. Using original modules is preferable to using OGG for size reasons. :)
You can get Skale here:
http://www.metamacro.com/awezoom/skale/
+BlackD
You can get Skale here:
http://www.metamacro.com/awezoom/skale/
+BlackD