Tried registering MPAudioSwitcher.ax and that fails with a return code of; 0xc0000005.
I can confirm the same error, with the mpaudioswitcher.ax dated feb. 24.
Tried with a mpaudioswitcher.ax file that i found on the messageboards here, dated somewhere in december,
and i can get this to register by hand.
however Installation of 1.2B fails even after manually registering the older file.
hth
Sadly I get the same error with that file.