what does this error mean?

what does this error mean?

Hello all,

I get this error message at seemingly random times when sending a 'begin'
query to the database.  I am using Postgres 7.0 beta 5.  I have a web-based
system based on postgres and each hit is a transaction.  

RelationClearRelation: relation 166124 deleted while still in use

The relation number is different every time.  
Does this mean the transaction is not beginning?  My 'hack' fix is to issue a
second begin statement if the first one fails... but that is really weird.

Thanks,
-Andy