I'm experiencing some strange mouse glitches when running a few different games in MS-DOS. The issue occurs when the mouse and keyboard are used at the same time (the worst example is in Command & Conquer, selecting multiple units with the Shift key while moving the mouse and clicking with the left button). The mouse pointer "sticks" to the edge of the screen and it's impossible to use it again. If I move the mouse around, the pointer jumps around to the sides and corners of the display. I usually have to reboot the computer to regain control again, but sometimes I can exit the software with the keyboard.

I've tried different mouse drivers to no avail (MS Mouse 8.20 and 9.01, WIndows 3.1 driver, CuteMouse 2.0). No luck with a different keyboard, either (I don't have another PS/2 mouse to test). Booting to a plain DOS prompt via floppy with no TSRs doesn't help, either. Occasionally, if I can close the errant program and get back to DOS, there will be some gibberish at the command prompt. I thought there might have a been an IRQ conflict, but MSD.EXE shows the mouse is on IRQ 12 as it should be.

Only certain programs are affected. C&C and Tyrian have issues. Warcraft 2 doesn't. DOS-mode programs also aren't affected (Norton Commander, MSD, etc.). If I run C&C in Windows 3.1, the problem goes away, but then performance suffers.

The system is a Compaq Prolinea 4/33S with NMB keyboard and Microsoft Mouse 2.1A running MS-DOS 6.22. This machine has dedicated PS/2 ports for mouse and keyboard; no add-in cards or modern hardware here. I had the exact same system about 30 years ago and don't recall experiencing this problem before, but then again, that was a while back 😀.

Any idea what might be going on? The only thing I can't rule out is the mouse itself, since I don't have another one to test, but I'm thinking it's a hardware bug that goes away in certain programs depending on how the mouse is interfaced with. Not sure if it can be fixed or not.