Association Class transformed into regular Class

[ClaudiaArchondo]

I created some association classes by dragging and dropping the icon from the toolbox. The packages are under Subversion VC. After some check-ins and check-outs, the Association classes were transformed into regular Classes. I now have this awkard situation where, for the same association class definition, if I double-click on the association link, I get an Association Class properties window and if I double-click on the class box itself (connected to the association link by a dotted line), then I get a Class properties window.

Any help?

Thanks,
Claudia