Sharepoint - 'WebForm_PostBackOptions' is undefined - NewForm.aspx

I'd like to first start off by confessing I'm a novice Sharepoint Administrator.

The problem our users are experiencing is that when they try to create a new discussion or respond to a thread in any of our discussion forums they, after pressing the ok to sumbit button, nothing happens...

We've tried this on different computers on both our internal and external network; users on the internal network are able to post fine while external users seem to be the ones affected.
I noticed that this happens in all browsers that we've tried (Chrome, IE 8+9, Mozilla) but in the IE browsers an error appears in the status bar and when clicked reads...
'WebForm_PostBackOptions' is undefined and underneath that 'NewForm.aspx'.

I have included a snapshot of the issue in hopes that it can explain things a bit more clearly.

I have read many posts on many different websites concerning this but none seem to remedy this particular issue, any help concerning this would be GREATLY appreciated!

Thanks in advance.

P.S. I forgot to mention we are using Sharepoint 2007 build  12.0.0.6545