Well, I tried it 3 more times, and I was not able to reproduce the problem with the modem. The problem of missing graphics was consistently reproduced, however. It didn't just affect the site I was connected to when I ran CCleaner (this one) either. Running it again after disconnecting did correct the problem. Cleaning again while still connected didn't help. So it seems my inability to dial up after my first test was a fluke, or a coincidence. I've been told by a couple of users that they run CCleaner while online, with no problems. So it doesn't affect all systems, is easily reversable, basically not much of a problem. Of course, I didn't try running the "Issues" scan while online, I'll leave that to somebody braver (or stupider) than me.