What is your OS on your HTC mobile phone? If it were Android, it might block the SharePoint 2010 Authentication popup window.
The first step is to simply grab the Firefox Browser from the Android Marketplace. Firefox is one of the browser officially supported by Microsoft for SharePoint 2010 and will allow you to login to your SharePoint site and login. Firefox
supports SharePoint’s login popup and allows you to login to your site.
For more information about SharePoint 2010 mobile access, check out the following article:
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