Fan control was working, now is not

I'm running #!9.04 on my acer aspire one with the default kernel.

I've also followed the posts in the wiki on fan control to install and load acerhdf at boot. Initially all worked as intended with the fan staying off until the netbook got reasonably warm.

Following a software update I noticed that the fan behaviour had changed and was remaining on. However if I type 'sudo acerfand' at the command prompt or execute 'sudo /etc/rc.local' this then turns the fan off.

The fan does go quiet during boot up but switches on again at the log in screen, which is annoying.
Any ideas what is going wrong with the boot up process or which log files I should be looking at?

(As a 'work around' - I've tried adding acerfand to the autostart file in openbox but it cannot execute without root permission and I don't know how to do this)