The current version of VOSI.biz client applications (version 1.2) are all 32-bit applications. The 32-bit applications should work fine on x64 operating systems. We have noticed that Windows Explorer integration doesn't work well, including drag and drop files from Windows Explorer to VOSI.biz File Explorer. You can still drag and drop upload / download files from VOSI.biz local pane to remote pane.
We are working on a native 64-bit version, which should fix the Windows Explorer integration bug on x64 based system.