I've been using pitbull for about a month now and I really like it. I have had this problem most of the time but just lived with it...mostly because I was tired of installing new unit frames.
After playing for a while, my target, TOT and sometimes character frame will start to disfigure a bit. Combo points will attach to the spark energy watch bar and sometimes an enlarged buff/debuff icon will take the place of a target frame.
I have noticed lately that sometimes I get a huge opaque square on my screen. It will take up nearly the whole screen and usually go away by hitting escape but sometimes not.
Relogging usually fixes the issues for a while but they tend to come back.