I'm waiting for the solution by 'Drifter'. Meanwhile I have disabled the "Build In Storage". In all those years I've never used the BIS so I won't miss it...
Get Total Commander:
- Go to \\\registry\HKLM\System\StorageManager\AutoLoad\PS M
- Open the key "Dll" by "double-tapping" the file
- Change its 'String value' to "PSMFSD.dll.xxx" and press OK
- Close Total Commander
Soft reset your device and the BIS has 'disappeared'. Now start TomTom and everything works as it should.
(I've installed TomTom directly on my device and the maps on a SD-card...)