A few weeks ago is also when we updated the message board software...

Caching by your ISP and/or your web browser of old pages / embedded javascript elements is likely the cause of the thumbnail problem ... I tend to lean towards your ISP as the cause since you indicate that both MSIE and Firefox are experiencing the same problem.

Next time when viewing a message with a thumb on it, press CTRL-F5 (MSIE) at the same time to force a refresh; not sure what the command is in Firefox. And do a forced-refresh on the main message board page at http://boards.cannabis.com/

Doing some forced-refreshes alone may correct the problem ... perhaps others here have some other suggestions for things to try.

Ron