500112 - Can't send mail out of Windows Explorer or any other application

Status: VERIFIED DUPLICATE of bug 499958

(Thunderbird :: OS Integration, defect)

Description

[Joe Dipierro]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.16) Gecko/20080702 Firefox/2.0.0.16
Build Identifier: Thunderbird version 2.0.0.22 (20090605)

"File - Send - Mail Recipient" from any application fails to send e-mail. 

Reproducible: Always

Steps to Reproduce:
1. Go to Win Explorer any external app -- WordPerfect, Acrobat, MS Excel, etc.; click "File, Send To, Mail Recipient."
2.
3.
Actual Results:  
A wndow appeared saying, "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 client."

Expected Results:  
Should have given rise to a T'bird "Compose" window, containing a new message (with attachment) to be sent.

I have checked that T'bird is still default mail client. It still is. 
This began just today, 1st day of Version 2.0.0.22 upgrade. No problem previously.
Willing to downgrade to 2.0.0.21 if I can find how.