When trying to upgrade an EPiServer 5 site to 6 I get a an error message:

Adding/Updating assembly redirect for EPiServer.WebParts
Adding/Updating assembly redirect for EPiServer.WorkflowFoundation
Adding/Updating assembly redirect for EPiServer.XForms
Adding/Updating assembly redirect for EPiServer.XmlRpc

An unhandled error has occured:
You cannot call a method on a null-valued expression.
When executing

At C:\Program Files\EPiServer\CMS\6.0.530.0\Upgrade\System Scripts\Upgrade Site
 (SqlServer).ps1:449 char:75
+ if ($wizard.SelectedApplication.ConnectionStringNode.providerName.Contains <<
<< ('Oracle'))

=
Get-EPiIsBulkInstalling
An error has occured and the transaction will be rolled back
Rolledback
Error - System.Management.Automation.RuntimeException: You cannot call a method on a null-valued expression.
   vid System.Management.Automation.ParserOps.CallMethod(Token token, Object target, String methodName, Object[] paramArray, Boolean callStatic, Object valueToSet)
   vid System.Management.Automation.MethodCallNode.InvokeMethod(Object target, Object[] arguments, Object value)
   vid System.Management.Automation.MethodCallNode.Execute(Array input, Pipe outputPipe, ExecutionContext context)
   vid System.Management.Automation.ifStatementNode.Execute(Array input, Pipe outputPipe, ArrayList& resultList, ExecutionContext context)
   vid System.Management.Automation.StatementListNode.ExecuteStatement(ParseTreeNode statement, Array input, Pipe outputPipe, ArrayList& resultList, ExecutionContext context)

The sitename does not contain any spaces like it suggested in this thread. 

http://world.episerver.com/Templates/Forum/Pages/thread.aspx?id=37925