I'm getting an error message whenever I try to start debugging.

This happens whether it's a windows or web project, newly created (vs2008), or existing (converted) vs2005 project.
Prior to installing vs2008, I had vs2005 and sql2005 installed (and did not uninstall them).
The vs2005 debugger continued to function properly after the vs2008 install. 

I've attempted all of the following, none of which have made any difference:

1. "repair" the vs2008 install
   
2. uninstall and re-install vs2008 (multiple times)
3. uninstall vs2008, vs2005, framework 3.5, 3.0, and 2.0sp1 ... then install vs2008
4. starting vs2008 with the /SafeMode switch
5. running the debugger from the command line: VsJITDebugger.exe -p <pid>
   ( it showed the vs2005 debug engine, but nothing else )
   
6. (re) register all of the dll's in c:\windows\microsoft.net\framework\v2.0.50727
   NOTE: all registered fine, except mscordbi.dll
   "regsvr32 mscordbi.dll" returned the following error:
   

   mscordbi.dll was loaded, but the DllRegisterServer entry point was not found.
   This file can not be registered.

Do you have a 64-bit or 32-bit operating system?

Could you try going to C:\Program Files\Common Files\Microsoft Shared\VS7Debug, and tell me what dlls you see and their file version? One way to do this is with filever (see http://support.microsoft.com/kb/913111 - filever.exe /v "%CommonProgramFiles%\Microsoft Shared\VS7Debug\*). You might want to also try running regsvr32 on all the dlls in this directory.

If that doesn't help, the only other suggestions I have would be to try gathering a process monitor log (http://www.microsoft.com/technet/sysinternals/processesandthreads/processmonitor.mspx) of file and registry activity during F5 and email it to me ('greggm' on the microsoft.com email server).

Thanks,

Gregg Miskelly
Visual Studio Debugger Dev

Thanks Gregg ... sent you an email with the information you asked for.

I just noticed something odd today ... my UserAgent string in IE shows 2 versions of the 3.0 Framework:

Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.04506.648; .NET CLR 3.5.21022)

Don't know if there's anything to that ... just grasping at straws.

Just a follow-up for anyone who may find this post after experiencing the same problem ....

I sent Gregg the "filever" list that he asked for and he spotted several .tmp files in that folder ... signifying that there had been a problem with the reboot after the installation.  He was further able to interpret the "filever" and spot the dll's that had not upgraded ( in my case, they were:  msdbg2, csm, and pdm ).

After making a backup copy of the folder, I deleted those 3 dll's, as well as all of the .tmp files ... then did a repair of the VS2008 install.

That did the trick ... I'm happy to report that the debugger in now functioning in VS2008, as well as VS2005.

Much thanks to Gregg for his assistance.