I am not sure when this started happening (can't recall if it was after an OS update, etc or not) but it occurs in both Firefox 1.5.0.7 and Firefox RC1 Beta.

This is what it looks like on some webpages. Notice the words "Mozilla" and "Firefox" in the fire search result are overlapping slightly



Here is another example from the mail page of Digg.com. Notice the last word before the "More" link and the link itself overlap.



When composing a message in Gmail you can delete text (right to left) and even though the cursor moves back and the text deletes it does not appear that the text deletes. Notice in the next picture it apears that there is still text after the cursor, but in reality that text was deleted. However if I were to copy and paste all the text from that box into a textedit document that text would not be there or if I send the email the text would be gone too



Here is another example from Gmail. This is what it looks like if I type a whole line and then delete it using the delete / backspace key