If you check the front page of the website you will see it says to use your public key.
This is not your address, your public key. You can get this by opening your client and going to console and running getnewpubkey p2pool, this will spit out a string, use that as your username.
The big paragraph at top says "Using your payment address as the username and any password". I realize it says to use public key for 2 of the coins down lower in the page, but people might not actually go down there and look. They might just read this top instruction, click the coin at top of menu bar, and then be mining wrongly. (Looks like 3-4 on your node are using invalid addresses atm.)
I'd suggest changing the top spot to read:
Using your payment address (for most coins, some require public key instead, please see blow) as the username and any password.
And on the rare coins that need public key, putting a notice on the top of those specific node pages too.
