axis2_http_sender.dll depends on linkinfo.dll (use Dependency Walker to see) and might not load on Windows Server 2008 because w3wp.exe cannot find this dll (use Process Monitor to see). linkinfo.dll is usually stored in %Windir%\system32 (c:\windows\system32) but not on Windows Server 2008. In order to get it there, install Desktop Experience feature.
Links and references:
Desktop Experience Overview
When you do not install the Desktop Experience feature of Windows Server 2008, programs that require programs that are included in Desktop Experience do not run