Funky RAM issue, always fails memtest86+ on test 7

Hey fellas. Got a strang one here. It's an MSI PT880 Neo (V2) and a P4 3000 I believe.
I originally ran the regular memtest86 and it failed at test 7 every pass, various places in the ram from the 13mb spot to the 490mb spot on a 512mb stick of Kingston 512.

Point is, I've tried about 6 different sticks of RAM and it always fails on test 7 in random places, with every stick. I've tried Kingston 512 DDR400, 256 DDR400. I tried Corsair as well. Then I tried different OTHER speeds like PC2100 256 and 512. Nothing works.
Then I starting running the newer memtest86+ and it also fails everything on test 7. I'm just running 1 stick at a time.
So I reset the BIOS in case there was some weird speed issue thing, didn't help, all BIOS settings are auto-detected. Always failing in test 7.

Why do you suppose memtest86 and mt86+ would always fail on test 7 on any stick of RAM? Besides a bad motherboard, is there any logical reason for this kind of error? I don't even know what test 7 is or what that could mean, guess I should do some research. But I thought I'd ask just in case anybody knows what this could be.

thx

P.S. Windows is not really affected except that recently, the customer says suddenly Windows will not open any programs. You can move the mouse and do basic things, but no programs will open, not even task manager, it just seems frozen, have to shut it off. I am guessing this could be because the RAM is acting up. That's when I found this issue.

Test 7 in Memtest86 does random 32-bit sequences (i.e., AE4F8BC1) and switches them frequently to see how the RAM accomodates the change of sequencing patterns. I don't think it's a software error since I've never seen anybody with a similar problem to yours. It could be a faulty memory controller. Do you have another motherboard where you can try the RAM on? This will tell you whether it is the motherboard's problem or RAM's problem.

I had an older motherboard that had a surge strike (even with a superessor) and then went bad. It was also an MSI. I looked at the capacators after the strike and noticed some bulges. This was after I developed chronic memory issues. slot two always failed.

The current MSI board I got works fine.