I have same problem. Actually, I'm using a per-object cache where the problem is detected. It's not a solution, but a workaround.
Edson Richter --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.574 / Virus Database: 364 - Release Date: 29/1/2004
