Since Apple has released Mavericks, Vectorworks 2011 no longer runs on Macs with 10.9 / Mavericks – although this has been widely criticised, Nemetschek is most likely to stick with its policy to only provide support for the last 2 versions of Vectorworks.
An overview on which version runs on what is available here.
Currently you only have the following options to deal with this situation:
1. upgrade to the latest version of Vectorworks;
2. downgrade your Mac(s) to 10.8 / Mountain Lion (if you still have an installer), we have done this successfully on a variety of models – however the latest MacBookPro11,2 series can no longer easily be downgraded and it is only a matter of time before the new iMacs can no longer be downgraded either;
3. if the above is too radical, setup a bootcamp partition as explainedhere.
4. use Fusion or Parallels to setup a virtual instance of 10.8 and run VW2011 inside that – we must admit this is not ideal as VW2011 seems to have some speed issues when virtualised…