[horde] Class definition of Horde_Cache_emcache not found - Revisted

[d.hill at yournetplus.com]

I'm still getting an error relating to 'Class definition of  
Horde_Cache_emcache not found' periodically.

I have added my email account as an admin so I could get the full  
error message. Being the content of the text is over 500Kb, here is a  
link to the text of what I receive periodically:

     http://mail.yournetplus.com/d.hill/Horde_Cache_emcache.txt

I've changed all of the sensitive information (E.g. server domain  
names and passwords) to protect the innocent.

Can anyone shed light as to what is going on? I have very little PHP  
experience to debug this issue.