how can i solve a error appeared in image below

[debianlam]

hi,
i have installed virtuemart 2.0.14 on joomla 2.5.8  but when i access to virtuemart component and try to add categories or products i have  error as shown in image below

could anyone give me a solution for that ?
thanks..

[jenkinhill]

I don't know about anybody else, but the image is too small to read.