Intermittently a specific customer is getting the error below after click Run to run a test in Test Studio on FireFox version 37.0.2. The customer just clicks Run a second time and it may or may not happen. I am unable to reproduce the problem and we cannot get direct access to his application.

Overall Result: Fail
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'30.04.2015 16:20:04' - Executing test: 'IBN_Test_20150423_11h40', path: 'IBN_Test_20150423_11h40.tstest.'
'30.04.2015 16:20:04' - Using .Net Runtime version: '4.0.30319.18444' for test execution. Build version is '2015.1.319.0'.
'30.04.2015 16:20:04' - Starting execution....
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'30.04.2015 16:20:40' - Using 'FireFox' version '37.0.2' as default browser. 
'30.04.2015 16:20:49' - 'Pass' : 1. Navigate to : 'http://XXXXXXXXX'
'30.04.2015 16:20:50' - 'Pass' : 2. Click 'ENSpan'
'30.04.2015 16:20:50' - 'Pass' : 3. Click 'LoginLinkTopLink'
'30.04.2015 16:20:50' - 'Pass' : 4. Enter text 'i.nimaga@xpert-technologies.ch' in 'BugzillaLoginTopText'
'30.04.2015 16:20:50' - 'Pass' : 5. Click 'BugzillaPasswordTopPassword'
'30.04.2015 16:20:50' - 'Pass' : 6. Enter text 'qsxt2010' in 'BugzillaPasswordTopPassword'
'30.04.2015 16:20:51' - 'Pass' : 7. Click 'LogInTopSubmit'
'30.04.2015 16:20:51' - 'Pass' : 8. Enter text '3500' in 'QuicksearchMainText'
'30.04.2015 16:20:53' - 'Pass' : 9. Click 'FindSubmit'
'30.04.2015 16:20:58' - 'Pass' : 10. Click 'BzShowBugColumn2TableCell'
'30.04.2015 16:20:59' - 'Pass' : 11. Click 'NewLink'
'30.04.2015 16:21:03' - 'Pass' : 12. Click 'Metis Smart SuiLink'
'30.04.2015 16:21:04' - 'Pass' : 13. Select 'ByValue' option 'Monitoring' on 'ComponentSelect'
'30.04.2015 16:21:04' - 'Pass' : 14. Enter text 'Ticked made with Telerik Test Studio' in 'ShortDescText'
'30.04.2015 16:21:04' - 'Pass' : 15. Enter text 'Please see the attached document.' in 'CommentTextArea'
'30.04.2015 16:21:04' - 'Pass' : 16. Click 'TableCell'
'30.04.2015 16:21:04' - 'Pass' : 17. Click 'Button'
'30.04.2015 16:21:05' - 'Pass' : 18. Wait for '1000' msec.
'30.04.2015 16:21:06' - 'Fail' : 19. Click 'DataFile'
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Failure Information: 
~~~~~~~~~~~~~~~
hwnd cannot be IntPtr.Zero or null.
InnerException:
System.ArgumentException: hwnd cannot be IntPtr.Zero or null.
   at System.Windows.Automation.AutomationElement.FromHandle(IntPtr hwnd)
   at ArtOfTest.WebAii.BrowserSpecialized.Firefox.FireFoxActions.GetContentRectangle()
   at ArtOfTest.WebAii.Core.Browser.get_ContentRectangle()
   at ArtOfTest.WebAii.ObjectModel.Element.GetRectangle()
   at ArtOfTest.WebAii.Controls.HtmlControls.HtmlControl.MouseClick()
   at ArtOfTest.WebAii.Design.IntrinsicTranslators.Descriptors.ClickActionDescriptor.Execute(Browser browser)
   at ArtOfTest.WebAii.Design.Extensibility.HtmlActionDescriptor.Execute(IAutomationHost autoHost)
   at ArtOfTest.WebAii.Design.Execution.ExecutionEngine.ExecuteStep(Int32 order)
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'30.04.2015 16:21:06' - Detected a failure. Step is marked 'ContinueOnFailure=False' aborting test execution.
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'30.04.2015 16:21:06' - Overall Result: Fail
'30.04.2015 16:21:06' - Duration: [0 min: 25 sec: 854 msec]
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'30.04.2015 16:21:07' - Test completed!