[plt-scheme] changed policy for native libraries?

Has the policy changed for when mzscheme loads a native library  
instead of an .ss file? I've updated to the latest nightly binary and  
all of a sudden the scheme-pg package won't load the native version  
of its back-end module. I've made sure the .so file has a newer time- 
stamp than the .ss file.

Help!

Thanks,
Dave