> Looks like your client stores compressed data in memcached. Check
> your client documentation to find out how to switch it off.
I already did that -- I'm sure it does not compress data.
I just noticed that the problem occurs only for pages with a lot of HTML (6KB), while smaller pages (3KB) are rendered fine. This is nowhere close to the 1MB limit of memcache. For this page http://konstruktors.com/ everything is OK, while this http://konstruktors.com/blog/ returns the garbled string.
I'll try a different PHP memcache library, but I really doubt that it will have any effect.