SQL 2012 install fails with 'Object reference not set to an instance of an object.'

Hi, I'm trying to install SQL 2012 RTM Enterprise on a Windows 2008 R2 single node cluster.

The installer starts goes through some checks and then fails with the message 'Object reference not set to an instance of an object.' It happens while the small 'wait while...' dialog box is showing, another window pops up briefly (I think the feature selection window - can't really tell as it doesn't draw before disappearing). Then the ‘Object reference not set’ message comes up.

From the summary log file..

Overall summary:

  Final result:                 Failed: see details below

  Exit code (Decimal):          -2147467261

  Exit facility code:           0

  Exit error code:              16387

  Exit message:                 Object reference not set to an instance of an object.

  Start time:                   2012-09-26 08:52:53

  End time:                     2012-09-26 08:54:08

  Requested action:             InstallFailoverCluster

  Exception help link:          http://go.microsoft.com/fwlink?LinkId=20476&ProdName=Microsoft+SQL+Server&EvtSrc=setup.rll&EvtID=50000&ProdVer=11.0.2100.60&EvtType=0x9AF1AE5E%400x44A889F9&EvtType=0x9AF1AE5E%400x44A889F9

…

Exception summary:

The following is an exception stack listing the exceptions in outermost to innermost order

Inner exceptions are being indented

Exception type: System.NullReferenceException

   Message:

       Object reference not set to an instance of an object.

   Data:

     HelpLink.EvtType = 0x9AF1AE5E@0x44A889F9

     DisableWatson = true

   Stack:

       at Microsoft.SqlServer.Configuration.RulesEngineExtension.RulesEngine.ShouldRuleRun(Rule rule)

       at Microsoft.SqlServer.Configuration.RulesEngineExtension.RulesEngine.IsRuleSkipped(Rule rule)

       at Microsoft.SqlServer.Configuration.RulesEngineExtension.RulesEngine.LoadRule(String ruleId, List`1 ruleProperties, XmlSchema ruleSchema, XmlElementParserFactory elementParser)

       at Microsoft.SqlServer.Configuration.RulesEngineExtension.RulesEngine.LoadRules(IEnumerable`1 ruleIds)

       at Microsoft.SqlServer.Configuration.InstallWizard.RunRuleProgressController.Initialize()

I have rebooted, tried different media, tried uninstalling the setup files and rerunning but always get the same result.

Any help would be gratefully accepted.

Thanks,

Bruce.