FYI, I'm having the same issue.
Did a fresh install of Windows 7 64 bit English and upgraded to Windows 8 64 bit English.
Installed Textpad 6.2.2 English.
Able to copy/paste fine in all other applications.
Able to copy with Textpad. Not able to paste.
I uninstalled 6.2.2 and installed 6.1.3. Paste still does not work. I haven't rebooted after the downgrade yet to see if it clears anything up.
Textpad 6.2.2 Paste function
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