Page SAVE button does not work

I have an absolute weirdo, which may or may not be down to FCKEditor - but if it rings any bells I would be interested to hear.

I have a Forum Page, containing Title, Forum, Body using FCKEditor, Comments and Attachments.

Most of the time it is fine, except when I put in the following paragraph:

<p>When entering dates for an Exhibition or Course it is necessary to insert the date at which it should be removed from the summaries in the right sidebar, separately from the repeat until date. This is due to a deficiency in the software, which may or may not get fixed.</p>

In this case when one presses Save at the bottom of the Edit screen nothing happens. Using Firebug there are NO Post or Get transactions at all. The same thing happens in IE7.

Any ideas???
Tony.