that message can be due to several different factors and can't tell without looking at your products.

That message can appear if you have no product name - which of course is unusual or if you've used some characters - like an ampersand - that google (or an xml feed) would reject.

If it is due to an amperand - change the & to &

And the list goes on - such as using non-English words sometimes with a accent mark and so forth.