endomorph1 - Without knowing more details (like what other inbound links you have), if I retained your current product page setup, I would probably nofollow the links on the foreign pages. I'm not a big fan of using internal nofollows, but I think that would be the cleanest way to do things.
You certainly don't want to disavow your own navigation.
Normally, Google allows a reasonable amount of cross-linking on one's own site, but with multiple language sites and 5000+ product pages all cross-linked, I can see Matt Cutts raising his eyebrows. Most likely, that much cross-linking would look like a "link scheme" to Google.
Regarding the question of whether the disavow would be hurting your own sites, it's noted in this thread that Google has said that disavow won't hurt friendly sites....
Best practices for using the Google disavow tool, confirmed Feb 3, 2013 http://www.webmasterworld.com/google/4542078.htm [webmasterworld.com]
"Do not worry about damaging other people, that does not happen"
That said, I think disavowing your own pages would unnecessarily complicate things... and possibly Google might not figure it out. To use a bad analogy, but one that comes to mind... it's something like trying to correct incorrect internal nav urls by using canonical link tags. It really doesn't make sense to do it that way.
Perhaps someone can suggest an approach that wouldn't create the PageRank black holes that internal nofollows would create, but which would prevent the appearance of a network of sites for the purposes of pushing link juice.
A far better alternative approach, IMO, would be to build product pages for each site, in the appropriate languages. As these would be in different languages, they wouldn't be seen as dupe content... and each site could be assessed by Google on its own merits.
