Error: Products are not shown

Some products are shown in the product lister but I was unable to retrieve this product when using the product reader.

In the front end an error message is shown ($GLOBALS['TL_LANG']['MSC']['invalidProductInformation']) and whatever I tried, I was unable to get the product information.

It took me some time to locate the problem, I looked at the tl_iso_products records in the database for different products but could not figure out why this does not work.
That is ... until I started changing the alias in the product's record. Apparently it is not allowed to have an alias that consists of only numbers - a bit of a shame since I had the part number as alias :? Guess I'll use "pn1234" instead of "1234" then ;)

One other thing I could not locate is the 'gid' in tl_iso_products.
For two products this was set to 1, resulting in grouping these products under a product group that was created automatically (at least I don't remember creating a group).

I'm guessing that product groups are still under development - or do I need to activate this somewhere?
This is a great addition - I have been playing around a bit with this and it looks great - can't want for this to be available as an editable item in my products.

Rob