I can see everything on my desktop, the task bar etc.. it's not my screen settings. I don't remember having this issue before the AH went down last night, but I also just began looking at items at this level so It's not for certain. I'm on a CRT at the moment and tried running the game at 1024 x 768, 1280x1024, and 1600x1200.. none of them produce any improved results when viewing the bottom item in the AH list for rare items lvl 50+.
I should add that the issue arises when I switch from searching via items for my character(Wizard) and sorting by Wizard only to view items of higher level. Items searched under Heretik(Wizard) come up fine and filter upwards.