Sametime is incompatible with Notes, insists on Outlook

Since upgrading to the Sametime Connect client 7.5.1 from 7.5 I am
getting a window. On it is displayed:
Microsoft Outlook
Either there is no default mail client or the current mail client cannot
fulfill the messaging request. Please run Microsoft Outlook and set it as
the default mail client.
OK
Pressing OK starts the Microsoft Outlook install wizard.
I went into Notes and ensured that it was set as the default client. I
set it to not be the default and exited Notes. I got back into Notes and
set it back to the default client and exited Notes. I've rebooted.
However it still displays this window when starting Sametime.
I am sure that it is Sametime that is bringing this up. Right now this
window is on my stacked icons on my task bar. It is stacked on top of the
Sametime Connect Client and has the same blue symbol often used in
cartoons to hold verbal text.
Sametime Client 7.5.1 Build 2007-04-16-16.14
Notes Client 7.0.2 September 26, 2006
Windows XP Professional Version 5.1(Build 2600.xpsp_sp2_qfe.070227-2300 :
Service Pack 2)

Rob Berendt