Problem swapping Languages

Hello,

After installing SEO package and i ask to auto create friendly seo urls tags etc , i cant swap from a language to another .
I have 2 language installed - Greek and English
When i am in English language, If i choose Greek (or Vice versa ) at Home,Category, product page I get that :
Sorry the item does not exist
and i have to refresh i order to see the product or category or home page at the language i choose .
After refresh is ok..

Any help ?

what kind of seo url mod are you using? Is there an extension being used?