If everything is 3.5, you may still need the 'family' update. It corrects issues with other .net version that may be in play depending on the driver etc.
If the reqs are right (=>3.5 .net and =>6.1 rd client)
then you may need this hotfix:
(there's no fix for 2008 R2 yet, but you should email the support folks and they say they'll help at no charge.
Here's the page:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;972600Direct link to hotfix:
http://support.microsoft.com/hotfix/KBHotfix.aspx?kbnum=972600&kbln=en-usIt may say 'not for this operating system'
Use 64 bit (of course =) for those OS units.
If the link doesn't work, try this one:
http://support.microsoft.com/hotfix/KBHotfix.aspx?kbnum=972600&kbln=en-us#step1