patching file downloader/template/connect/packages_prepare.phtml Hunk 1 FAILED at 33. 1 out of 1 hunk FAILED -- saving rejects to file downloader/template/connect/packages_prepare.phtml.rej
I apply the patch SUPEE-5994 first as required, but the issue came up anyway.
First solution :
Download a fresh version of magento 1.9.2 and replace your packages_prepare.phtml with the fresh packes_prepare.phtml file from the zip.
Then reapply the patch. Instead of "FAILED" you will have the same issue with "IGNORED" because the file already exist with the right content.
Second Solution :
Download a fresh archive of Magento 1.8.1 here : http://www.magentocommerce.com/download/noregister
Replace your current packages_prepare.phtml file with fresh one from this archive.
Apply the patch again, and it will works.