Could you please confirm that the hook described on that line is pmdata_postsave?
If so, I don't believe vBShop hooks anything on that page, so this would appear to be a conflict with another mod that we have no control over
Please go into your Plugin Manager and look for all other mods that uses the hook you find on that line (most likely pmdata_postsave), then disable them one by one until you find the culprit. Feel free to report back here even if it turns out not to be a DBTech mod at fault so that we can give speedier responses in case other customers have similar problems