Problems with Apache running mod_pagespeed. "Invalid Request!, No data Saved"

[GeorgeI]

Hi

After a forced server reboot over the weekend due to a power outage, any attempt to login to Roundcube mail (version 0.5.3?) gave the error message "Invalid Request!, No data saved."
After reading some support issues I cleared my browser cookies and the error message changed to "Your browser does not accept cookies". Which was not true.

So I tried upgrading first to roundcube mail 0.6 and then 0.7 beta. All gave the same problem.
All browsers I tried, firefox, explorer and the browser on my android phone all had the same problem.

Then I remembered that the Google Apache plug-in mod pagespeed had updated very recently and I had had previous issues with the module and a Drupal installation before.
So I tried disabling mod_pagespeed completely and all worked OK.

I then tried disabling mod_pagespeed just using the .htaccess file but without success.
I am currently running with mod_pagespeed enabled, but disabled in the Apache config file for the domain Roundcube mail is running on.

I did not have the time to determine a working fix modifying just the .htaccess file in the Roundcube base directory but there should be one. I might try again when I have a bit more time.

I just though this might be helpful information if anyone else has a similar problem.