NSF Directory Pool Full - Why?

i know there have been various posts here about directory pool / buffer pool full error messages.

What actually causes the problem though as surely just upping the memory allocation is nothing but a “quick fix” and there must be some other underlying problem?

Any ideas on this - we are using 6.5.1 and have got the error in the subject line…

Subject: NSF Directory Pool Full - Why??

We have this problem on 6.5.1 also. Upgrade to 6.5.2 (released June 1, upgrade already!). That solved the problem for us.