Content plugin not triggered

[drizzt99]

Hi,
I have J2.5 with VM 2.20 ( I tried upgrading, but all my products were deleted and the language fix was irrelevant as the products were missing in all langages).
Anyway, here's the thing:
Until 2.2, I was able to setup a bunch of images in the content, and a content plugin (multithumb) was triggered to take care of the images.
The problem is - for some reason the plugin is not triggered anymore.
Here's what I did:
In productdetails view.html.php, I've set up the code to retrieve the product images, and enter them into the "$product->text" variable.
I can see it is supposed to be triggered ($results = $dispatcher->trigger('onContentPrepare', array('com_virtuemart.productdetails', &$product, &$params, 0)) but for some reason, the multithumb plugin is not triggered any more.
Any idea what changed and how I can fix this? or maybe some other way to show images in a nice thumbnail view + browsing with the fancybox?
Thanks