CMS Made Simple Forums

Hi,
A few days ago I upgraded from 0.13 to 1.0.2, all went well.
The day before yesterday I was away somewhere and used a PC with IE 6 to try and edit something, listontent.php gave me a 'XML not valid ' or something to that extent, error when I tried to expand the list view. I was in a hurry so I thought I'd try at home later and everything would be fine probably.

Today when I try with Firefox to access the 'pages' , Firefox  opens a pop up window saying:
you have chosen to open listcontent.php , which is a php document waht should firefox do with this file, and gives me an option to open with an app or save to disk. All other browsers, IE 6 etc, give errors too.
The rest of the CMS can be accesed o.k. and works fine.


I have tried to empty cache, and overwritten the listconten.php with the one I still had on my machine, fiddled around with prefs,  this did not help.
Any suggestions to what I can do to resolve this ?

Update:

I overwritten the files again to see if that would help, but I get the same error .

Firefox wants to download the listcontent.php and the rest shows up fine.
Does anyone have any idea what I can do? Is it possible to downgrade the CMS? 0.13 was working fine

(EDIT:
I've searched the forum and read that downgrading is not really a very good idea.)

Can anyone help with this problem?

EDIT : solved. I contacted my  host , turned out it had something to do with the way PHP was configured, not the CMS.