Just updated lmde this morning (mostly nvidia stuff) and it pulled in and installed a -486 kernel as a dependency! (the same kernel version as the existing kernel, just the different architecture).
I tested both the -486 and the original (and correct) -686 kernel and both worked normally so I decided to remove the -486 version, but synaptic wouldn't remove it without removing the -686 kernel image, which didn't seem like a good idea.
I then attacked it with aptitude instead of apt and this removed it without any bother and everything works OK.
Not exactly a problem or a bug, but a strange piece of behaviour none the less, so something to look out for if you have nvidia graphics.
Fujitsu Lifebook AH532 Laptop. Intel i5 processor, 6Gb ram, Intel HD3000 graphics, Intel Audio/wifi. Realtek RTL8111/8168B Ethernet.Ubuntu12.10 (Unity), Mint14 (Cinnamon), Manjaro (Xfce).