boinc client = 5.10.45
computer = vista dual 1.7ghz with 2 gb ram.
"it" = whatever research project it's running when it does this.

Version 5.10.45 has permission issues v.v. the Screensaver and the client service install (something related). Basically, the SS can not hook into the core client to get is graphics feed. Could be your Firewall or AV doing this too. Exceptions on port 31416 and IP 127.0.0.1 need setting for BOINC.scr, BOINC.exe BOINCmgr.exe.

Under 6.2 there are still sporadic old issues with the SS which got fixed as of 6.3 and hopefully this is permanently put to bed when WCG finishes testing 6.10 and promotes this as the endorsed client (end of December objective).

So, as suggested, change the SS to something none BOINC related and you win CPU cycle as well. CPU cycles BTW can be controlled with the 6.2.28 kit of WCG as are the Frame refresh rates.

Let us know.

edit: I'm better than a spell-checker