Submit a new story, hit Back button and get "Webpage has expired"

[psref]

I'm using Pligg 1.0.0 RC 4.

During Step 2 of Submitting a New Story, if the user entered incorrect data or forgot to fill in a required field (say they forgot to select a Category) and click "Preview and Submit", they get an error message like "No Category Selected" (which is good) with a Back button. When the user clicks the "Back" button on the page to fix the mistake, they are expecting to be back at Step 2, but instead get "Webpage has expired".

Is this a problem with a PHP setting?

Thanks,
Dave

[Yankidank]

Upgrade to RC5.
Can submit without selecting category | Pligg CMS Projects

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I upgraded -- RC5 fixed the issue. Thank you!