When I hit Alt-P on a paragraph or equation, the preview uses an excessively tiny and pixelated font (see attachment).
TeXstudio 2.8.2 (hg 4641:bc57cde57758) for xUbuntu 12.04 64 bits
Xubuntu 12.04 64 bits
texlive 2009-15 (seems old, but it's the one that came with the distro repositories)
works fine here.
Have you tried to use another preview method (instead of preview with dvipng) ?
by the way, it uses your latex preamble. If there a small font is set ...
Thanks. Changing the preview engine from "dvips" to "pdflatex" solved the issue. I don't have dvipng installed so I guess TeXstudio defaulted to the next available option, which was dvips.
Maybe the default should be changed to use pdflatex if dvipng is not available, as dvips seems to produce the poor results I showed (at least for me) and the solution wasn't too obvious.
probably the default will be changed some time