I began having this same gmail issue last night. The email loads but the body of the message is blank. Saved messages and receipts are also blank. Gmail still works fine in IE and Chrome. Have not changed any setting. Using Firefox 8 Beta Update.

I found my problem. In Options > Advanced > Encryption > Validation, the option "When an OCSP server connection fails, treat the certificate as invalid" was checked.

Perhaps the update to Firefox 8.0 caused this to be selected.

Sadly this did not solve my issue. Glad your problem in resolved.

Box not checked, problem continues. This is apparently a Firefox 8.0 issue; gmail works fine in Chrome

Try clearing cache and cookies, sometimes this simple procedure is the one that works.

I've solved the issue for me. If cmargoli's solution doesn't work for you, perhaps mine will. The problem for me was an old subscription to Ad Block Plus. For some reason, it was detecting the body of the emails as an ad and blocking it. You can check to see if this is your cause by temporarily disabling ABP for Gmail and seeing if the problem is solved. If so, you can permanently solve it by simply updating your ABP subscription by going to: Tools>AdBlock Plus Preferences>Filters>Update All Subscriptions

Now just reload the tab for gmail and you're done. Hope this helps some of you,

To fix this problem go to Firefox, Add-Ons, Add Block Plus Options, Filters, Update all subscriptions.

The Add Block Plus subscription must be updated.