when trying to cancel a trade a get a invalid action notice Error: The action specified does not appear to be valid. If you believe otherwise, please restart the action by going [Back] and reloading the previous page. i have attempted this with firemaw and abomination on two separate trades( firemaw on one trade, abomination on a completely different trade) and when attempting to cancel both trades i get the same invalid action text. no one i know seems to be having this problem. I'm using Firefox. bug does not occur on google chrome
Since this only happens on firefox for you and I just tested it on firfox without any problems it is likely that you need to clear your browser cache. Here is Mozilla's breakdown on how to clear the cache https://support.mozilla.org/en-US/kb/how-clear-firefox-cache