Well, i dont think my problem are invisible walls, because sometimes when im flying i get past this "invisible walls" to then return to where i was 2-3 seconds ago. This started happening on after i changed to the Horde, on Icecrown. Im not sure if its only on my main character or the 3 that i moved to Horde, since i changed a week ago and mostly played the rogue (achievement hunting and stuff).
Sometimes i cant keep flying because im stuck in the air and sometimes i keep flying and the UI gets kinda bugged, it dissapears, doesnt load some things, etc. Then i get teleported back to where i was before.

Anyone had a similar problem before? If so, any enlightment would be greatly appreciated.

Thanks in advance!