Some things that you can put on the cart seem to affect the ID codes. I dont understand why, but going to an older version or moving to XGpro or NeoMax software to format usually does the trick.
Occasionally I bet a slim loader bites the dust. Or even perhaps in the software transitions there was something else entirely going on: reinserting the cart enough times into the slim loader could have disloged some dirt/dust/tarnish off the cart connectors...
I can say that older combinations of NeoMax + NeoPowerKit caused conflicts with drivers, making such errors.
Are you certain you uninstalled your NPK and NeoMax before upgrading them to 2.1/1.5 versions? It leaves behind some "junk" in the registry if you just dump a newer on on top of the old one, which affects the next install...
It'd be really nice if there was a standalone DOSish app that did not rely on NPK or NeoMax, which all it does is format the cart...
I did clean off the cart connector w/ alcohol and contton swab..but I dont think that was it,and I did try to clean the slim loader as well. If this is the case there has to be a way of making your own loader cleaning tool.I remember back in the day that they had something like that for the original Nintendo.
The last thing that was burned on the cart before any of this happened was a rom of Final Fantasy III which was all messed up when you try to play it so it may very well have been that. Although,after copying menu 4 back to the cart (with great relief) and flashing Dawn of Sorrow and playing for awhile,I hooked it back up to my Win2k PC and this time it was giving me the cart error messages again

Is it possible for me to get another Slim Loader to see if mine has just burned up,I've only had it about 3 weeks now and if anything I could let you know if that is what the problem is and not the software. I did stick my nose on the Slim Loader and could smell a hint of burn,but I dont know if thats normal or not because it is new. For now I think I am going to stay away from trying to flash roms direclty onto my cart so that way I can at least still use it with menu 4.
On to a question about MK2/3 (BTW these are all from the 1GB Neo Power Kit) I flashed menu 4 onto the MK2/3 from the SD card then tried booting directly off the MK2/3 cart with Mario 64 inserted without the flash cart in the GBA slot and got nothing but white screens. Is there any patch or other software that will let my boot off of that directly? I have a gray DS and probably newer firmware and I dont think I want to take a chance on flashing my firmware.