Sorry Patchou but this problem persists on 4.50 too so I decided to post it here in case some others can reproduce it (I thought you couldn't until now)

I can reproduce this on my two computers, one is XP home, the other is XP professional (without any theme or any other program like WindowsBlinds) so can you people reproduce the bug you see below? In setup's Sponsor page, if you use ampersands to select "Install sponsor" or "Don't install sponsor", the bold formatting on those options disappears. Also in normal Plus! windows lke preferences, if you use ampersands on options, the background of options turn to a grey color. Remember sometimes it works fine, but half of the time, the problem appears, so give more than one try to reproduce it please.

Known bug, and has been reported since a long time and just recently again. But the threads are in the beta testing forum... So anyways, thanks for confirming.