When trying to use our JIRA instance we keep getting lots of
permissions errors which makes JIRA very difficult to use. If we keep
trying then eventually it works. This has been happening for about the
last week or so.

It's very annoying as you keep having to enter the issues of the JIRA
you're trying to raise. Then you get an error when you press "Create"
and so you have to start all over again and enter the details again.
It can often take 10 attempts to create the JIRA.

Sample error messages;

XSRF Security Token Missing

Your browser has not provided any parameters at all and your input has
been lost. Press back now to try and resend the data. This is most
likely caused by a bug in the browser. FireFox 3.6.0 have been known
to exhibit this behavior. For more information see this bug report
http://jira.atlassian.com/browse/JRA-20696 JIRA could not complete
this action due to a missing form token.

You may have cleared your browser cookies, which could have resulted
in the expiry of your current form token. A new form token has been
reissued. Problematic action: CreateIssueDetails.jspa JIRA
administrators Please refer to this page for details on disabling form
token checking.