Error on saving form settings

On a specific form I get an error when I try to save the settings. it displays this: There was an error while saving your form. Please contact our support team. And does not save.
It does save when I change other stuff like deleting a field. It just doesn't save the settings like the confirmation message.
Other forms on the same site save fine and it's a rather simple form. So I am a bit mystified. I tried copying the form and exporting/importing it again but the error persists.

I'm using GF 1.6.4.5 and wordpres 3.3.2. Can this be due to the minor uptrade from 1.6.4.2 (I think) to 1.6.4.5?
Any ideas? I can send a form export if you like...

It's on it's way.... thanks for having a look...

Hi David, thanks for looking into it. After your message I spent yet another hour digging into this and found out that somehow another plugin is interfering specifically with this one form only.... really weird. But that solved my problem for now. I just turn off that plugin, update the form and than turn it on again. A bit shaky but it works for now.
You're welcome to have a look, but I guess it's not Gravity Forms but the other plugin that is doing some weird interference...

Thanks again...

Hi David,

I just noted your question. Sorry for my late response. I have been away for over a month.
But actually it's not worth looking further into it. It's a very specific single use plugin. (http://wordpress.org/extend/plugins/nomis/)

many greetings,

Han