Since a recent power failure that occured when, among other programs, AVISynth and foobar2000 were running on my PC, these two programs are causing trouble. AVISynth refuses to run entirely, and foobar can't load two components any more (soundtouch and ID3v2). The strange thing is that both problems disappear when I give my account administrative privileges. The permissions of the affected files show no restrictions, and the two foobar component DLLs are entirely readable even when foobar cannot load them.
I have tried deleting and re-installing both AVISynth and foobar, which didn't change anything. I also ran Scandisk with the 'correct file system' option enabled, without success.
I'm really at my wit's end here. Any ideas? I use W2k SP4 with an NTFS HD.

Strange stuff. No idea why that could happen, but you could try to play with the registry (with regedt32) - access permissions apply to the registry entries too. If there are any entries regarding foobar2000 or AVISynth, find them, and make sure that they have no restrictions set for your account. Also, it may be that some other components (maybe some system DLLs) used by these programs became restricted. Search the web for tools like DependencyWalker, ProcessExplorer, RegMon, FileMon, PMon, DebugView, and RegCleaner - they might be helpful in finding what's going wrong.