Hello James.
I normally use FastCGI and APC, but just to try to reproduce what you are seeing, I enabled xcache and disabled APC. The result is that everything runs fine, no such error. Is it at a particular path that you get this?
If it matters, this is stock PHP 5.2.4 that comes with Ubuntu Server LTS (8.04), and the Xcache from their repository as well (1.2.1).
FastCGI is running under Apache 2 using fcgid.
So I've been trying this for a couple days now and I get this error:
Fatal error: Cannot redeclare field_flush_caches() in
/../d7/modules/field/field.module on line 134
It only happens when using fastcgi and xcache. xcache and mod_php have
no problem and fastcgi without xcache is also fine. It seems to be
related to the autoload functions but I can't for the life of me
figure out why. Google has been very little help either. Anyone have
any idea what's going on here? bug in xcache?