I un-installed all the Nokia software on my PC, re-booted, and installed a fresh copy of PC suite.

The stuff I un-installed during this process included:

Nokia ovi suite
Connectivity cable driver
Ovi suite software updater
Nokia software updater

After installing PC suite, and re-booting again, I can see the icon for PC suite on the taskbar.

Points arising: the instructions should presumably say "un-install" all Nokia software before updating.

I connected the phone via USB cable, and on my PC I can see my contacts and calendar directly from the N900, when I attempt to do a backup of the phone's status, the PC suite software says "No phones connected connect your phone now" - which is totally illogical. (because I wouldn't be able to see my contacts from the phone if my phone connection wasn't working).

Simple Nokia software, running on a bog standard 32 bit software platform, not working.