To be fair, that hasn't happened in a pretty long time for me - but in the earlier days it was commonplace. It used to be bleeding edge features that would do it, other times it was just because they took so long, that interrupting the process of upgrading or installing caused a mess. Or installing the newest version alongside the older version, etc.
Visual Studio is a massive and complex creature (much like other "big IDEs", such as Eclipse) - although it has become much more streamlined in more recent releases - considering how complex it is.
EDIT: To be clear, problems often involved corruption of registry values, library/DLL hell, small database or configuration files and caches, etc. that happened with Visual Studio in the scenarios above.