Scary font replaces regular in acrobat

[siriusb]

Hi,
I have aobe acrobat 7.0 pro. When i view most of the pdfs, if I try to zoom-in/out or scroll-down, the font for the entire dcoument changes from the normal font to this:

The change occurs at the redrawing place, that is, at the bottom or at the top while the unredrawn place remains normal. If I scroll down/up to cover and then uncover the normal place, it wud've change too. This is not happenning with some pdfs though, however fast i try to scroll or zoom in/out.
This is a fresh install and no option was changed. I have forceware ver 71.89. But I have the same trouble with the previous versions as well. Infact i had the same problem with ati card as well. OS is Xp pro.

[Choto Cheeta]

well same problem here.... the Acrobat reader 6.0 works fine with my XP SP2.... but when i install Adobe Acrobat 7.0.... there is some font problem with my system also....