Amiga 3000 with jerky mouse and icons switching to monochrome green

[Oldsmobile_Mike]

Two thoughts right off the bat:

- I don't think the jerky mouse pointer and green screen are related.  You're looking at two, or possibly more, separate problems.

- Have you tried with both the 23-pin video output and the HD15 VGA output?  Is the problem the same on both?  Any difference?

- Open it up and check for battery damage, stat.

Okay, that's three things.  But I'll repeat that last one again - check for battery damage, if it's a barrel battery, remove it asap.  

[Oldsmobile_Mike]

Where can I find a 23-pin video output cable?

This is the standard video output of every other model of Amiga.  The 3000 is unique in that only it contains the native circuitry for 31KHz "VGA" video output (the 15-pin connector).  I just assumed you must have a few old Amiga monitors kicking around, most of us do.  

The previous owner checked for battery damage and reported that everything was fine. He sent me a picture and it looked fine. To remove, do I just pull it off and leave the empty holes?

There are some settings that are unique to an A3000, these links might help you:

http://www.amiga.org/forums/archive/index.php/t-15710.html

http://members.iinet.net.au/~davem2/overclock/batt.html

Personally I'd just pull it off, replace it with a better one.  Barrel batteries kill 3000's worse than just about any other system, due to their location on the motherboard.  I'm sure some folks will say go ahead and leave it if it ain't leaking yet, but since you never know if it might start leaking tomorrow... an ounce of prevention is worth a pound of cure, and all that, right?  

Are you able to boot off a Workbench floppy disk?  Do the same problems occur then?