Cannot send any e-mail messages "The operation failed. An objectcould not be found"

Hello,

I have been having massive problems with Outlook 2007, as of late.

After having solved my initial problems with this programme (constant
crashing when adding .pdf files, for example), I am now facing a new
ordeal; whenever I try sending a message I constantly get the message
"The operation failed. An object could not be found".

I have tried several options to resolve this issue. Among those:

1. Adding a new profile.
2. Deleting my old profiles.
3. Running the scanpst.exe
4. Running Office Diagnostics.
5. Re-installing Outlook. De-installation is not an option as I am
running the entire Office 2007 package.
6. Looked into the registery but found nothing out of order.

I have tried countless solutions, so much so that I really cannot
recall them entirely.

I would appreciate any help. PLEASE!!

P.S. Outlook initially would not even start until I installed Eudora.