If you use '' in the attribute list to describe a product, the +10 (for example) will not update the products price.
So if your describing a 7'' by 2'' (+10.00) sticker, don't use the '' otherwise the +10 will not work. Just type it as 7 x 2 or 7 inch by 2 inch.
Hope I described that well enough for a fix!
Same with colon ":". Colon does not have to be specified in product attribute, as VM already puts one in.
Maybe relates to this: http://dev.virtuemart.net/redmine/issues/129
This has been fixed in SVN and will be included in 1.1.6, due to released soon.