[ic] Undefined Catalog

[Matt]

My Catalog is down now with this error for the second time in one 
week.  It looks like my host upgraded IC last night,... so I'm 
guessing during the restart it crashed (it was working prior to going 
to bed last night - only created new categories anyway).

What could I be doing to cause this error?  I've searched months back 
to find that several people are having this error, however what to do 
to fix it and prevent it doesn't seem to be very known.

Are other users getting this consistently?  

Thank You

Matt