"island_classics"
Something must have changed in the ASCOM platform that is causing this issue, it has always been possible in the past to set a zero time bias exposure and it makes no sense that ASCOM is blocking this because the camera does allow for zero time exposures when taking bias frames.
You are using an old an unsupported version of MaxIm, v5, which as not changed in years, and the QSI ASCOM driver has also not changed recently however I am able to to reproduce the same problem in both MaxIm DL6 and DL5 with an error message stating an impermissible exposure time has been requested when attempting a bias exposure, irrespective of the exposure time set in MaxIm's Camera Control window, whether "greyed out" or otherwise.
The only software recently changed on my test system is the upgrade to ASCOM platform 6.6 SP2 however I haven't used my QSI cameras for over a year and I don't know when this problem appeared, also, I have always used the native QSI CCD Plugin for MaxIm in preference to the ASCOM driver anyway, so maybe this problem has been around for a long time?
I think the quickest and easiest solution for you is to abandon the QSI ASCOM driver in MaxIm DL V5 and swap to the native QSI CCD plugin instead, which I know works in all exposure modes in both MaxIm DL V5 and DL V6.
The only thing to be aware of when using the native CCDPlugin in MaxIm DL5/6 is that it allows you to set exposure times that are shorter than the shutter can operate.
If you set an exposure shorter than 0.03 seconds for a "light" or "flat" then the camera will just return an empty frame because the shutter does not open.
If you download the plugin file linked here from my Google drive and copy it to your MaxIm DL V5 program folder (while MaxIm is not open), then after plugging-in the camera and starting MaxIm, from the Camera and Filter wheel setup dialogues in MaxIm's Camera Control window select "QSI Universal" as the camera model instead of ASCOM and follow the setup dialogues to configure both the camera and filter wheel settings that are presented when using the QSI plugin for MaxIm.
Note that you must select the "QSI Universal" native driver for both camera and filter wheel when you setup MaxIm, you can't mix-and-match.
The location of MaxIm's program folder is normally C:\Program Files (x86)\Diffraction limited\MaxIm DL V5.
You should not see any errors with exposure modes or exposure times when using the QSI Universal native camera plugin for MaxIm in preference to the ASCOM driver.
HTH
Will.
WILL B