I saw this bug too - I am pretty sure it is not in xchm. I first saw the same raw html behaviour in the help reader included in boa-constructor (which uses similar wxgtk libraries).
I created a new user and both xchm and boa-constructor work fine when logged in as that user. I solved the problem by comletely deleting my ~./mime.types file. It was filled with entries created by crossover-office. I tried deleting just the chm entry but no joy. There are a bunch of html variant types registered that may be the offenders. Since I always run crossover from the command line, this shouldn't bother me. Hope this helps.
