Activated plugins mysteriously deactivated

Hello,

This is my first post.

I am running wpmu 2.7 with plugin management handled by plugin commander and plugin manager.

All plugins are in the plugin directory apart from supporter, mu branding and domain mapping which I placed in the mu-plugin directory

Other plugins used include:

multi-user plugin manager, plugin commander, Admin Footer Text, Contact Form 7, modified Great Real Estate, NextGEN Gallery

These are activated per blog as required.

The issue:

I have created a main blog ok and also created another real estate blog that runs fine as well. On trying to create a third blog, when I activate the required plugins, there are automatically deactivated again.

Just wondered if anyone else has had a similar problem.