Gmail displaying annoying error about full cache

When I upgraded to Internet Explorer 7, on Windows XP SP2, I started getting an error on gmail which says

Your browser's cache is full and may interfere with your Google Mail experience.

Since clearing my cache did not help in the slightest so I tried a few other things.

• Tools > Internet Options > Advanced tab. make sure that “Do not save encrypted pages to disk” is unchecked.
• Tools > Internet Options > Browsing History Settings, Change “Check for newer version of pages at every visit” to "automatically". This originally worked for me but then something happened on my laptop and then it started again.
• The size of my cache was sitting at 1024MB so I lowered this to 250MB. (From Browsing History Settings again)
• The final thing I tried ended up getting rid of the error. I added mail.google.com to the list of allowed sites.
• Somewhere advised that deleting your temp Internet files and recreating it might help but I didn't try this, nor can I advise if it works.

If anyone has anything else that can be added please leave a comment and I'll add it in.

UPDATE: The message came back after adding mail.google.com to my list of allowed pop ups. After further rooting around I found that if you access gmail through https://mail.google.com/ using secure http the message disappears. As far as I'm aware you still need to go into your internet options on explorer and ensure that “Do not save encrypted pages to disk” is unchecked.

This poses a problem if you access your gmail through google toolbar however, google allows you to edit the xml behind the custom buttons such as gmail. Here's what you have to do in order to get your gmail button on your google toolbar pointing to https://mail.google.com/.

• Click the settings button on your toolbar.
• Click on "Custom Buttons"
• Find the gmail option and click "Edit"
• Click "Advanced"
• Press ctrl + f and search for http://mail.google/ and change all instances to https://. There should be 3 urls you need to change.
• If you like, you can change the message you get which tells you that you have new gmail. Search for or just and between the tags, put something like, "Hey bawbag! Check your email."

You can also do this "advanced edit" in forefox's google toolbar, however firefox doesn't cause gmail the confusion that internet explorer does.

UPDATE (again) - gmail now offers you the option under "settings", to always use https. Tick this option and this whole problem goes away which is good because the iGoogle gadget still takes you to the http: site.