I had a similar problem that drove me, everyone on this board, Sony and my computer manufacturer crazy for a week or so.
It turned out to be a corrupted font file.
I had installed an older version of Microsoft Office after installing Vegas Pro and that started the problem.
Did you install any other programs after you installed Vegas Pro? Perhaps a word program or something that has it’s on font files?
I also found that as I used other programs this same problem became noticable on them as well.
If that is the problem you may have to do a “restore” to your computer which means you may have to re-install all your programs. I’m sure that is not what you want to hear, but it solved my problem
Good Luck!