I receive compiler error C2666 ("number overloads have similar conversions") in files G4UIArrayString.cc and G4VUIshell.cc in interfaces/basic on Windows NT under Microsoft VC++ 6.0 when attempting to build libG4UIbasic.a in the cygwin make environment. The documentation (http://msdn.microsoft.com/library/devprods/vs6/visualc/vccore/c2666.htm) mentions that this is caused by improved compliance to ANSI C++, and will cause code which previously compiled to now throw an error.
I assume that this problem is fixed since a long time.