FWIW - My observations on various problems
Missing Attatchment button - fixed by flushing cache on one of my machines, the others were ok.
Posting a msg/replying - didnt notice any problems
Last visited time - seems as I would expect,gets correctly reset on next login if I click Log Out, or exit and wait about 15 minutes.
Logo background image with Christmas Hat appearing/disappearing-
Flush cache and start from http://www.iceinspace.com.au/ - No hat
Flush cache go directly to forums http://www.iceinspace.com.au/forum/ - Yes hat
As the files have the same name whichever is loaded in cache is then always used until flushed.