Hi Rob,
You're definitely having issues downloading components from the web. You should download the offline installer from http://software-dl.ti.com/dsps/forms/self_cert_export.html?prod_no=CCS6.0.0.00116_win32.zip&ref_url=http://software-dl.ti.com/ccs/esd/CCSv6/CCS_6_0_0/. Make sure you extract all the files from the zip, clean out the install folder you used previously (or use a new one) and run the installer as administrator from within the CCS6.0.0.000116_win32 folder.
Danish