VpxClient has stopped working

I have recently received a Windows 7 64-bit lenovo laptop for a new job. It has all of the latest Windows updates installed (including .NET 4)

I installed the vSphere client (first 4.1, then 5.0) seemingly without issue. When I attempt to launch the client (either version) I immediately get a Windows notification that "VpxClient has stopped working" and I can either check online for a solution or close the program. Either way I cannot go any further.

Checking in the vpx log files I find these entries:

[        :startup :W: 1] 2012-08-14 15:43:12.418  Log for vSphere Client Launcher, pid=1252, version=5.0.0, build=build-455964, option=release
[        :Error   :W: 1] 2012-08-14 15:43:12.478  System.UnauthorizedAccessException: Attempted to perform an unauthorized operation.
   at Microsoft.Win32.RegistryKey.Win32Error(Int32 errorCode, String str)
   at Microsoft.Win32.RegistryKey.SetValue(String name, Object value, RegistryValueKind valueKind)
   at Microsoft.Win32.RegistryKey.SetValue(String name, Object value)
   at VpxClient.Program.RegisterClientMimeExtension()
[        :Error   :W: 1] 2012-08-14 15:43:12.487  A fatal unhandled error occurred in vi client
[        :Error   :W: 1] 2012-08-14 15:43:12.491  System.TypeLoadException: Could not load type 'shipEntryFieldId.IList' from assembly 'mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'.
   at System.Windows.Forms.Control.OnVisibleChanged(EventArgs e)
   at System.Windows.Forms.Control.SetVisibleCore(Boolean value)
   at System.Windows.Forms.Application.MarshalingControl..ctor()
   at System.Windows.Forms.Application.ThreadContext.get_MarshalingControl()
   at System.Windows.Forms.WindowsFormsSynchronizationContext..ctor()
   at System.Windows.Forms.WindowsFormsSynchronizationContext.InstallIfNeeded()
   at System.Windows.Forms.Control..ctor(Boolean autoInstallSyncContext)
   at System.Windows.Forms.ScrollableControl..ctor()
   at System.Windows.Forms.ContainerControl..ctor()
   at System.Windows.Forms.Form..ctor()
   at VpxClient.FormVpxConnect..ctor()
   at VpxClient.Program.Main(String[] commandline)

If anyone can offer any assistance it would be greatly appreciated. I have spent several futile hours searching and attempting various fixes.