Firefox Error: Timed Out wpt.2.7.1

Dear,

I have a Private instance - Amazon Ec2 - Windows 2008 R2 - 64Bits running with wptdriver for Chrome and Firefox.

When the server is rebooted and I start a test with Chrome browser the test runs OK.
When the server is rebooted and I start a test with Firefox browser the test received timeout and the time to load the page test is too high.
When I connect with a remote desktop and run another test with Firefox browser everithing is OK. When i disconnect the test runs ok too (sure I receive the black screenshot because I ve connected with the RD).

When I reboot the server the problem with the Firefox come again.

Please, do you know whats going wrong with the Firefox browser?

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thank you and tell me if you need more info.

Looks like onload isn’t firing. Can’t tell you why but does it happen for all pages you test?