Setup Failure Codes/PHP Magic Quotes runtime off
The page identifies a major configuration problem. DAViCal might appear to work somewhat but major functionality will be broken until this is resolved.
See PHP Magic Quotes GPC off for more background.
Suffice to say that if you love backslashes then this option is for you! Turn it on and before you know it you'll have events full of backslashes!
We're kind of "backslash-haters" here at DAViCal central, and we think everyone else should hate on this option too.