Steps to recreate the issue...
1.) Login to any of our internal Websites (C#, ASP.net 2.0) and pull any Crystal Report exporting Excel
2.) Save the Excel document in XLS format on your local drive somwhere
3.) In Excel, goto the Insert -> Comments menu option
4.) Excel will error out and give you a debug screen
All Web Servers are Windows Server 2003 R2 Standard Edition
User workstations are all running WinXP, Office 2003
Sites are developed using C# ASP.NET VS2005 w/ Crystal Reports rpt's embedded right into the .NET project
Merge Modules used are C:\Program Files\Common Files\Merge Modules\CrystalReportsRedist2005_x86.msm
I have asked the question in the MSDN forum.
http://forums.msdn.microsoft.com/en-US/vsreportcontrols/thread/5b966f67-7ae9-418e-92ec-21096b979f99