1.5.4 after it's been running for several days will just shut down..turn-off without warning...
Strange... Do you mean, it shut down each time when it was running without a break for several days? Or do you mean that you first installed it a few days ago, and it shuts down?
Did you check the closing options in F2 > Browsing > Tabbed browsing?
I wonder if you have some mouse gesture or shortcut key, perhaps even from another program, that closes windows...?
By the way, do you see keyboard shortcuts in the menus?
If not, click F2 > GUI appearance > Display keyboard accelerators in menus.
Then look at File > Exit K-Meleon, if that command has a shortcut and which.
Mine is Ctrl+Alt+F4 (=AltGr F4), probably default, but not sure.
My guess is that perhaps you often click F4...?
Ah yes, and have you tried with a second profile, with default settings?
But to be truly default, you must also move all macros in the profile macros folder.
Or test with a second, pure portable installation, independant from the setup version you perhaps are using?