Strange Bug

[archos]

I notice a strange bug after migrating from VM2.0.0 to VM2.0.1f on Joomla 2.51.
After the upgrade, the first product (unique ID=1) on my category was no more visible.
I checked the « published » option, checked the DB table, everything was ok.
I create a dummy product because I was thinking the problem could be from the number of items to be shown on the page but my dummy product was visible...
After looking every possibility I really had no clue.
Then I decided to clone the « invisble » product, and then the cloned one works flawless.
I again compare column by column the DB table and I'm still not able to see any difference except of course the unique ID.
Before the upgrade this product was visible.
I was using the original views from VM2.0.1f

PHP 5.3.8
Mysql 5.5.16

PS :    I still have the original (not visible) and the cloned products on the DB if somebody wants more info.