Suddenly on my N800 with OS2008 I am finding a process eating up around 86% of my cycles. The process is telepathy-gabble.

Killing it stops my gtalk so it must be connected with gtalk.
I have made no changes to gtalk settings recently. The only changes I have made are installing the combined audio and backlight status bar icon , and the new status bar clock. I cannot see why either of those should affect gtalk settings.

Can anyone suggest what might be happening?

I observed the same interesting thing, after the same installations, but I had also removed the Contacts applet to make room, and expected that was to blame.

Hmmmm....

My problems are also coincidentally with some problems that my provider (Virgin/blueyonder) are having with emails and slow web access.
Are you by any chance with Virgin?

No. University WiFi here.

Try setting your Presence to offline, then starting it again. It has to do with the Contacts app and backend (telepathy) and tends to happen to me when I connect (or try but fail) to dodgy access points. Killing it will just cause it to respawn most of the time.

Now that Virgin (my ISP) have sorted themselves out the problem seems to have gone away. So nothing to do with the status bar icons.
If it happens again I will try the setting presence tip.
Thanks for that.