able to publish but unable to open form in Sharepoint portal server 2003

[JD]

Hi,
I created a form using Infopath 2003, and was able to publish it to my
sharepoint.
Everything looks fine but when i try to fill in the form i get an error
stating: the form cannot be made, Or the program is not installed or the
template cannot be opened.
When i go into the settings for the library i can open the template itself.
Could this be because in the meanwhile Office 2007 was installed with
Infopath 2007.
The portal server is still version 2003.

Thanx
Joeri