I solved this problem after an hour of work, so I’m sharing my solution.
I installed PDFCreator version 1.0.2 on two PCs (Win7 x64 and WinXP sp3 x32). In both installations, nearly all pdfs I print are gibberish when I use the internal Ghostscript (version 8.70). This happens for pdfs printed from every application except Microsoft Office programs. Other Microsoft applications (like IE) create gibberish pdfs, too. Even the Windows “print test page” utility creates a gibberish page using the internal Ghostscript.
The current version of GPL Ghostscript (8.71) solves this problem. Using that, I get good pdfs printing from ALL applications I tested, and also the Windows “print test page” utility. The PDFCreator blog says it reverted to Ghostscript 8.70 due to problems creating searchable text. But I have no trouble with that.
The current GPL Ghostscript is available here: www.ghostscript.com.