Which Build (Help > About) are you seeing this on?

I have the same problem. It's been running for several hours.

"C:\Users\v-dgit\AppData\Roaming\MediaMonkey\MM.DB"
"C:\Users\v-dgit\AppData\Roaming\MediaMonkey5\MM5.DB-journal"
"C:\Users\v-dgit\AppData\Roaming\MediaMonkey5\MM5.DB"
"C:\Users\v-dgit\AppData\Roaming\MediaMonkey5\MM5.DB.temp"

Then I get errors:
The database seems to be corrupted. Attempt to fix it ?

Click Yes

Then more errors:
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Application Error
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Application throw an exception Access violation at address 016120FF in module 'MediaMonkeyEngine.exe'. Read of address 00000000
Would you like to restart MediaMonkey in Safe mode?
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Abort Retry Ignore
---------------------------

Tried safe mode and got the same results.

And where are your MM databases? The MM4 database, and the new .MM5 db that you are building? Are they on the PC where you are running MM5?

That's not the normal time it takes. Do you know from which version you're updating and which version of MediaMonkey 5 did you install?

"Your Library is being upgraded to the latest version. It can take up to several minutes" is deceptive when it has to rebuild the library.
With 300,000 songs in my library, it can take at least a day to rebuild the library. I am up to 16 hours already
I just started using MM5. Are upgrades going to be a regular occurrence requiring rebuilding of the library?