Yeserday I opened a Visual Studio 2013 project file with the current beta (4.2.3 build 51) and was able to create binaries (I only use Xamarin to compile binaries for Linux. I am doing the rest in Visual Studio Ultimate.
Today I get the following error:
"Package creation failed. Der Versionszeichenfolgeteil war entweder zu kurz oder zu lang." in English "The version part is either too long or too short"
Just found the solution.... The first line was empty (so a "/n" and then "Microsoft Visual Studio Solution File, Format Version 12.00"...
Maybe you just would check for that??