If I play an avi file with SAMI subs turned on (an additional external file
with a smi extension) and switch to fullscreen mode, the progress bar in WMP
10 is not functional, I can't jump forward/back. In order to do that, I have
to leave the fullscreen mode.

It seems the problem is not on my side, but
rather a restriction imposed by WMP itself. Does somebody know how to
circumvent this or can somebody at least explain to me why this annoying
restriction was built in? I seem to remember that WMP 9 did not behave this
way. Does somebody know whether this restriction is still present in WMP 11?