I'm running iPhoto 9.2.1 and OS X 10.7.5.
I've tried delete key alone, delete in lots of combinations withg control, alt, command, both delete keys, etc.
I get a message that says I have to import the photo first. If I do that it just puts it into my computer's iPhoto and leaves the other in Photo Stream.
Feeling really stupid and frustrated.
You need to update iPhoto. The latest version is 9.4.2.
To do your updates, do the following:
How to do software updates via the apple menu - http://support.apple.com/kb/ht1338. - is a link to Apples article on updating the software on your computer
If you need info on your apple ID -
You can visit the Apple ID Support page - http://www.apple.com/support/appleid/ - to learn more about your Apple ID, or visit the - Apple ID Frequently asked questions page - http://support.apple.com/kb/HE37.