Well now this is on VIrtuemart search feature that is requiring the category here.
Actually thinking further about it, missing categories would cause incorrect SEF urls.
I recommend you set a category for every of your published product. Even if you call that category 'uncategorized'
- Need help? Post the URL of the related page (eventualy as confidential info), it will help solve your issue faster.
- An error, notice or warning? report the exact message including the line number
- If you get a white page , enable error reporting and / or check your server error logs.