[cesarb]

> some software package to be installed, presumably in the interest of security, which injects a dll into every process on the machine

You don't even have to get that far. Shell extensions (for file open or save dialogs) and printer drivers also introduce arbitrary DLLs to your processes. And some of them are compiled in an old version of IIRC Delphi or Turbo Pascal, which on the DLL startup code unconditionally changes the floating point control word to something which causes unexpected behavior in some framework you're using.

(We ended up wrapping all calls to file open or save or print dialogs with code to save and restore the floating point control word, just in case they had loaded one of these annoying DLLs.)