virtuemart doesn't work after reinstallation

[trickyk]

Hi,
I recently started a test site with Joomla 2.5.9 and Virtuemart 2.0.18a. However, after encountering some difficulties with pricing and image size, I wanted to use an earlier version of Virtuemart (that worked for me before). Instead of first checking how to properly deinstall VM, I just started deinstalling all VM modules, plugins, etc. This of course has now caused major problems. I of course could not install an earlier version of VM , as the path to the VM2 component still existed. I therefore decided to again install the VM 2.0.18a. And although I can see the modules/plugins and I can also see VM under the component tab, I get a server failure message, probably because something is wrong with the configuration. As I am a beginner when it comes to VM, I really hope someone can help.
Thanks in advance!