If you don't specify a folder, then the current directory for the SourceSafe action will be whatever the current folder is at the time that step runs (which will depend on the current directory when VisBuildPro was started, 'Tools | Application Options | General | Set current directory to project folder after loading or saving projects', and/or whether a Set Current Dir action was previously executed). The VSS Get help [1] states:
The Get Latest Version command places files into the current folder. Used recursively on a project (the -R option), VSS gets all the files in the project and subprojects, and places them into subfolders of the same name. If you set the SS.INI variable Force_Dir to Yes, subprojects go into their respective working folders instead of into subfolders of the same name.
So your best bet would be to set the VSS Force_Dir INI value (you could also try setting the current directory in VBP before the SourceSafe step, but it might not be enough).
[1]
http://msdn.microsoft.com/library/en...sgrfSS_Get.asp