Same problem, and I have more information to provide.
Of course I can't completely represent you in your situation, but I will provide what I have.
Please take a look at this, generated by NirSoft's SimpleProgramDebugger:
Obviously, Warband gave up after loading WINNSI.DLL; it just quietly unlinked everything and exited without reporting errors.
After profiling another Steam game (Terraria), I found out that two dlls, "steam.dll" and "steam2.dll" are supposed to be loaded, as observed here:
I also noticed the two exceptions, 0x4000001f and 0x406d1388, but those two showed up with Terraria as well, so they are not the problem.
After some snooping around, I discovered that 0x406d1388 is involved in starting a new thread. Combined with the attempt to load steam.dll, I'm guessing Warband tried to communicate with Steam, but Steam refused to do so. Warband handled that exception, so down it goes with a nice 0 and nothing else.
My attempt to open mbw_workshop_uploader.exe further proved that. mbw_workshop_uploader.exe flashed a cmd window that says, character for character:
Steam is not open. Please open Steam
Here's some general info that wouldn't help anyone:
Windows 8 - 64 bit - Steam - Warband 1.165 - No DLC.
Of course, I'd rather go bother with the people on Steam about this, but the M&B forum over there is full of little kids who are incapable of any brain function. And of course, there would be no way I can get into contact with actual Steam developers and convince them to get their excrements together.
Finally to OP, if you think we are on a different boat, I have no problem removing my reply and starting a new topic. I only posted here because the forum rules urged me to do so.