WordPress and template files

Hello,
I am currently on a blog over WordPress 2.8 and I want to apply a specific template file on a page of my blog. The template file is well recognized when editing the page, but if I leave an empty template file (except from the name of the template of course), WordPress still understands it a s a blog’s page.
I recently did the same procedure with WordPress 2.7 and it worked fine. Has anything been changed with WordPress 2.8?
Thanks in advance for your help!