Hello Martin:
If I install a Vboxmouse.sys driver dated after version 5.1.38 (I tried several, including the last 7.0.6), exactly the error you explain occurs.
I tried several of date before that version and they did not give me error.
It can be significant, although it can also be associated with another parameter that I ignored.
I do not remember changing anything especially. I keep with REM the AMOUSE.SYS and USBMOUSE.SYS lines in CONFIG.SYS (VMOUSE.SYS is not modified)
I am using the maximum resolution 1920x1080 16Mc, with GRADD, according to the recommendations of the forum,
Panorama gives the same error with the same criteria, I have also tried it.
I hope that it would be useful to someone.
Greetings.