Totally stumped on this one, I have no problems whatsoever on windows 7 with Wrye Python 03a, Wrye Bash 288 and the new BOSS
On windows XP I thought it could be read/write permission related - I have checked I have the registry setting to override custom folder settings, opened a command line and applied attrib -r /S /D recursively to all relevant paths where files are affected. Cleaned out and re-installed Wrye Python 03a, Wrye bash 275 installer followed by an overwrite with 288 (previously just tried without the 275 installer, but knowing that using the 275 installer prior to the latest Wrye bash had solved a problem before gave that a go aswell).....
Stumped, I still get the stdout error, meaning I have everything working as expected but just cant get to the Installers tab - Which renders my primary installation method useless. It goes through the motions of refreshing/re-scanning all files, crc checks - but at the end of the progress I hit the stdout error and the installers tab does not display. Its stuck with the installers tab selected but still showing the mods tab info.
From what I can tell, Windows is throwing an error when WB tries to start 7z to read your packages, hence the windows error code (14001). The only other time I've seen this (not related to WB or Oblivion) was when I tried running an app that required one of the MSVC Redistribuables.
Firing up http://www.dependencywalker.com/ shows it needs msvcrt.dll to run, so looks like that's you're problem. I can't tell you which MSVC redist package you need, but you can find them on the M$ website http://www.microsoft.com/downloads/en/details.aspx?familyid=a5c84275-3b97-4ab7-a40d-3802b2af5fc2&displaylang=en.
I'm not sure if this is a change for 7z, or something that's come up in recent releases but hey *shrug*. I'd try installing the redistributable package and seeing if that works.