Netbeans class path inconsistancy
 

I've been having problems with Netbeans recently, in that whenever I create a new java project it's inconsistant about creating a class path.
I'll write my class then when I come to compile and run it I'll occasionally receive the message <No main class found>.

I discovered that when this happened I'd need to go to the Ant settings within the run panel, and manually select the class path to the project. I would then need to go to
file > project properties > run and set the main class.

I didn't find much on Google that helped me with this. So I was just wondering if anyone else had experienced this? And if so, did they find a way to permanently fix it?

Thanking you :)

Edit: Just to be clearer, I want to add that I always check 'Create main class' and 'Set as main project' when I create a new project.
Thanks.