Hi again, here some conclusions i got, unfortunatly i'm not good with java so i've not be able to spot the problem...

1. It add a 0,01 for every 1,00 (1,00 will became 1,01 - 5,00 will become 5,05...)
2. It doesn't effect the cart process, if you add product in the cart the price are right and all is fine.
3. Maybe the problem is in the jscript_ajax_updater.php
4. I try it on Mysql 4.x and 5.x with same results.
5. It effect only the product page. (Think because the module just work with it...)

no other hints at the moment :-(