I created a Product Type and added 5 parameters.
In a subsequent session, I created 2 more product types and added 2 parameters to one of them.
In the Product type list form, I checked the box at the left of the row for the two most recently added product types and clicked the 'Remove' button.
Both of the checked product types remained undeleted but the one product type that had not been checked was deleted.
I subsequently attempted to replicate the problem by checking the same box again for one of the remaining product types and pressed the 'Remove' button. This time, neither record was deleted.
Tested with nightly build from 24/3/2008
Extended Layout
Joomla 1.5.2
Apache 2.2.8
MySQL 5.0.51a
PHP 5.2.5
Regards
Phil