ADO notification

[Nigel]

I'm using query notification to call me back when there are changes on a
table. This all works fine on one of my tables , how ever what I would like
to do is for it fire on MSmerge_contents.

When I change the Sqlcommand to run a select from that table however I
immediately get called back with the info field of the
SqlNotificationEventArgs set to "invalid".

I'm, using the same from for SqlNotificationRequest from:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnvs05/html/querynotification.asp

Any ideas on what could be wrong?
tia