Could it be a conflict between your normal screensaver and seti trying to work at the same time. Seti kicks in when your normal screensaver would. Try turning off the normal one, and let the seti one take over.
'I have SETI@home set to run as my screen saver, but it keeps getting interrupted right after it starts running. What's going on?
The SETI@home client may be being interrupted by another screen saver or screen saver-like program. As SETI@home is designed to be as noninvasive as possible by only using your computer while it is idle, if the client detects another program that wants to run, SETI@home will quit and step out of the way.'
or in this case, not detect the normal screensaver starting and they 'compete'