primary key problem sql server

[Alessandro Colantoni]

Hi
I'm using ojb 1.0.1 with sql server.
 When I store an object, and then I delete it directly on the db I can't 
insert it a second time.
 Before storing I use to check if an object with the same key exists.
ojb doesn't detect any object with the same key (correctly... I deleted it)
But when storing it catch a sql server exception because primary key already 
exists.
Is it a limit of microsoft sql server (it keeps primary key somewhere?) or 
I'm doing something wrong?
thanks for help