Nope, not normal.
Can you give me a detailed explanation of what you’re doing? Which emitter, which property, graph window in main interface or in emitter properties dialog, etc. Stage emitter or while editing library?
Have you tried the “run with software rendering” option in the Start menu? If that fixes the problem it’s actually an OpenGL issue and you need to update your video drivers.
Also, if you haven’t restarted your computer lately, do that. Weird problems like this are often fixed by a reboot.
Alan.
http://www.wondertouch.com