What's wrong?
a) You eitehr have very little RAM as Todd already said.
b) You have enabled OpenGL for the comp vieweer and set your acceleration options for effects to use it, which will invalidate the RAM cache and attempt to render everything live.
c) Your project structure is such, that some pre-comp or otehr element updates whenever you scrub, which could be either an expression calculates a new result or some footage being pumped into the media cache.
d) You have something going on with audio and your audio hardware is misconfigured.
e) Similar to b), an OpenGL driven third-party effect like Magic Bullet Looks may be misbehaving.
f) Your graphics card is misconfigured, causing general redraw errors that invalidate the cache, possibly also related to OpenGL.
g) An input device driver e.g. from a tablet, some CoDec or otehr such thing is acting weird.
Check all these things and flip the relevant switches where appropriate and update any outdated drivers. Some combination is bound to resolve this.
Mylenium
