Dragging Mouse over Text in Document Temporarily Distorts the Words

I like to highlight text in a document with my mouse as I go sentence by sentence (not with the highlighter tool, just simply dragging my mouse over the words). For some reason, this is causing the words on the page to totally get screwed up.

These are the different things that happen:

1) It will spread out the paragraph to random parts of the page

2) It will show text from a different page over the part I have highlighted

3) It will be change size or even be unreadable.

Please note that it is temporary as it goes back to normal fairly quickly, but it makes it impossible for me to read while highlighting with my mouse.

*I have pretty much unchecked everything in "General" that could potentially cause this. The only other area that I feel could play a role is the "Page Display" section of Preferences. That is just a guess though.

Please HELP!