First attempt to comment on a jira results in "the issue no longer exists"

The steps to reproduce are more or less:

• I get a mail from jira about a created/udpated issue
• I click on the link, Firefox 3.0.6 opens it
• I comment on the issue, submit the commit
• the result is "the issue no longer exists"
• go back, the comment is lost, pull some hairs, rewrite the comment. This time submit succeeds

Workarounds I've found so far:

• before submitting, copy the comment in the clipboard, make it fail, go back, paste, submit, works
• when the page opens, force a manual reload of it, then comment

I believe the issue is restricted to Firefox 3.0.6, but haven't actually tried with other browsers.