Posted by Bill on October 30, 2000 at 23:46:46:
I took a look at Lee Oskar.com's site and found a reed problem chart on line with their harmonica repair kit info. File the base makes it flat and the free end sharp. I may be that your were filing the wrong reed.
Take the covers off you chromatic, blow the note in question and look in a mirror to see which reed is vibrating or use the tip of you finger to find it. As each chamber has 4 reeds, this could be the problem.
It may be that for some reason, chromatic's tune differently that diatonics! I put the problem on the message board below this. Sorry, lost your return email address :P
Bill