Maximum # of messages?

[Hanser, Kevin]

I have IMP v2.2.3 running w/an oracle8i backend, and it has been running
fine for months.  However, we have a mailbox that has 11500+ messages in it,
and I'm getting a strange error all of the sudden.  When I click on the
double arrow to go to the last page, it immediately tells me "you've got
mail" and continues to pop up the new mail message every so often, even
though there aren't any new messages coming in.  	I noticed the status
bar (at the top) was missing the # of messages readout, and upon further
inspection, I noticed this error message:

Warning: Bad message number in
/usr/local/apache/virtual-hosts/webmail.shopsforme.com/horde/imp/status.php3
on line 73

Have I reached a maximum message count?  Or could this mailbox be corrupt
somehow and IMP is just showing the effects?  This mailbox is kind of an
archive for incoming messages, that's why it has so many messages... so
deleting them is really not something we want to do.  
Ideas?

Thanx

Kevin Hanser
System Administrator
Merchant Internet Group
kevin@MerchantInternetGroup.com