Gnome 2.8 file association problem

[Richard Quint]

After a clean install of Fedora Core 3 I changed the default application 
to open html files from Epiphany to Firefox.  After doing this I no 
longer can open an html file by left double clicking or by right 
click->Open.  Right click->Open With still works.  When I do right 
click->Properties I get the file association dialog with radio buttons 
to change the default application (Firefox, Epiphany,Xemacs, ...) but 
changing the default has no effect.  Also the Delete application button 
is greyed out in the dialog.  This hasn't effected the default 
applications for other file types-e.g., left double-clicking a text file 
opens it in gedit. Where is the setting kept?

A second Gnome question.  I have tried googling for help on how to 
associate a particular type of XML file (known by its extension) with a 
default application without success.  Anyone know how to do this?  The 
application is Maple 9.5, which saves its worksheets as XML files with 
the extension .ms.

Richard Quint
rquint at vcccd.net