Sorry I forgot to get back with you all. I found the answer that worked for me.
I Googled around and found out that file association changes are kept in RAM (don't ask me why)
which means that the change is flushed out during a logout and the file
associations revert to defaults.
I discovered a command called kbuildsycoca which makes changes permanent by
writing them to configs or something like that.
I used kbuildsycoca --noincremental
The noincremental option = "Disable incremental update, re-read everything."
From kbuildsycoca --help-all
Worked like a charm for me, hope this works for you all too
P.S. - this worked for me in both Mandrake 10 and Slackware 10.
P.P.S. - After posting I realized that I had forgotten to mention that you needed to make the file association change first then issue the command 'kbuildsycoca --noincremental' in CLI. That's probably a given, but I wanted to be sure I was clear.