Problems with Bold/Italics/Underline

I am having a problem that only happens occasionally. Sometimes when I am
typing a document, I will hit CTRL-B (Bold) and I will release it, the bold
icon will light up then immediatly disappear as if I had never pressed it in
the first place. This also applies to Italics and Underline. Usually exiting
word and re-entering solves the problem, but then of course it comes back. If
I hit CTRL-B and type very rapidly afterwards it will stay on, but then at
that point hitting CTRL-B will shut it off for a second and then immediatly
shut it back on... Any ideas?
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