emacs badly recolors syntax highlighting on refresh

[Micha Feigin]

I started getting a strange behavior lately and I am not sure what I
changed that started causing it and was hoping someone may have an idea.

I have syntax highlighting turned on (global font lock mode). When I
first type in the text it is properly colored. If I press C-L or switch
buffers, it is then not recolored properly.

For example, doing #include <math.h> will color # in white, inlude in
blue and <math.h> in peach (the colored used to be different but they
changed to). If I press C-L the whole line is colored in purple.

I am using the themes package, but I haven't changed anything with it
lately.