Not sure which file this is in.
But when I ad a new VM Category, the string MOD_VIRTUEMART_PRODUCT_CHOOSE should be MOD_VIRTUEMART_CATEGORY_CHOOSE.
Ref to the language file language/en-GB/en-GB.mod_virtuemart_category.ini
There is also a misspelling in the Add Product module.
MOD_VIRTUEMART_PRODUCT_SHOW_ADDTOCART_DES should be MOD_VIRTUEMART_PRODUCT_SHOW_ADDTOCART_DESC