Faced this issue while running eseutil.exe in repair mode (eseutil /p) on Microsoft Exchange 2003.

First of all repaired mailbox database:

• Opened command prompt
• Changed folder to C:\Program Files\Exchsrvr\bin\
• run: Eseutil /p D:\EXCH\priv1.edb

Repair was successful. Then tried exactly the same steps for public folder database:

• Opened command prompt
• Changed folder to C:\Program Files\Exchsrvr\bin\
• run: Eseutil /p D:\EXCH\pub1.edb

But repair was failing with errors:

unable to find the callback library jcb.dll (or one of its dependencies). copy in the file and hit OK to retry, or hit Cancel to abort.

Operation terminated with error -2102 (JET_errCallbackNotResolved, A callback function could not be found) after 77.0 seconds.

Solution was to copy jcb.dll to following locations:

D:\EXCH (Exchange Database folder)
C:\WINDOWS\system32

I believe C:\WINDOWS\system32 would have been sufficient.