error 500 - product modification

[nick2011]

hello dear members
I am trying to edit an existing product coming from a quickstart package of Joomla!, but I always get a 500 error.
I've tried to google a little before posting, without success.
Please help.

[Jörgen]

Joomla, VM and PHP version

Jörgen @ Kreativ Fotografi

[jenkinhill]

What is the error - this may help to show the error source:  http://forum.virtuemart.net/index.php?topic=121692.0

Quickstart packages are often badly configured.  You may not be set as vendor for the product.