Just a little update on the issue, in case someone will find this useful:
I've tested the laptop with an Intel 2100B from a Dell laptop, and the problem still manifests, so I think it is safe to say that the 2915BG is not at fault, since the 2100B was sold in the low-end model of the C300 several years ago.
Another thing of interest is the fact that if you disconnected the antenna cables from the card, chances are the mouse jumping will cease. When using the 2100 I had to disconnect both cable, and distance them from the card. Naturally, that completely eliminated reception. However, with the 2915, I disconnecting the black cable seemed to do the trick for most of the time, so perhaps it is the black cable that runs by the inverter, thus causing problems?
In either case, when I brought the disconnected cable(s) close to the sockets(?) on the card, or touched them, there was pretty much 100% chance that there will be some interference leading to fake clicks on the tablet, and therefore to the mouse pointer jumping.