2 Problems after Upgrade PT9 to PT10: "Controller-Personality MBox3" and "MP3.dll"

[Eviltubbie]

Hi there,
I used to work with PT9 and an MBox 3, connected via USB. No problem so far. Yesterday, I upgraded to PT10.0.1. The installer requested to deininstall PT9 first. So I deinstalled PT9 and installed PT10 and 10.0.1-Patch. I also installed latest MBox 2 Driver (Version 1.0.19).
After starting PT10 I get an error, saying in German:
"Beim Laden der Controller-Personality MBox3 ist ein Fehler aufgetreten".
In English it means "An error occured during loading Controller-Personality MBox3)".
I ignored that to see what happens next. I opened an existing session and tried to bounce it to MP3. Next problem occured, saying
"Die MP3-Option kann nicht aktiviert werden. Grund: Modul-Initialisierung fehlgeschlagen für MP3.dll. Möglicherweise ist der MP3-Demo-Zeitraum abgelaufen".
In English it means "MP3 option can't be activated. Reason: Modul-Initialisation failed for MP3.dll. Probably MP3-Demo test timeframe has expired".
I started working with PT9 last year and haven't had an earlier version. So I did not have to buy the MP3-Option so far. And in PT9 I never ran into this problem.
The Controller-Personality-Problem is new, too. I checked Windows Device Manager and Mbox is installed correctly.
Then I uninstalled ProTools and MBox-drivers and started reinstalled the whole stuff. This the same 2 problems.
Additional info:
My Windows system drive is C: (it's an SSD). PT is installed on D: in a subfolder: D:\<folder>\Avid\... I checked "D:\<folder>\Avid\Pro Tools\DAE\Codecs\MP3" and I found an MP3.dll there (Version 10.0.1.58 from 19.01.2012).
I really appreciate any help because I'm running out of ideas and have to to some recordings with PT during the next days.
Thx in advance,
ET