As the error suggests, The Pulse installer can't create a virtual adpater on your system and like Kita mentioned there could be multiple reasons for this, most of them external to Pulse Client (related to the OS, another third party software, etc) The debug logs from Pulse might give a little more detail. Here is a shot in the dark: We had a couple of customers resolve this recently by following http://support.microsoft.com/kb/3024777 - If you are using Windows 7 then it might be worth a try.
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