Upgrading the Mac OSX

Just got my imac today, lurverly!! after an hour or so it decided to download all the required updates which is fair enough, after about an hour of download it started trying to install the updates at which point....nothing, just sits there saying configuring system for update for ages and ages and the progress bar doesnt move, after 20mins - half an hour I thought something must be up, so done a full restart, and the same again when trying to install the update.
Am I being to impatient? or is something up? can anyone help?
cheers

what update is it loading

10.5.5

sorry, its 10.5.6 combined

im running on 10.5.4, do I really even need to upgrade?

I usually manually download the combo updates and run them from the disk image, a better method, especially if you are getting problems

But I would run a permissions repair first using MainMenu

Santa Software | MainMenu

Mac OS X 10.5.6 Combo Update

Agree with loiushen. Download combo updater from Apple web site, drag to desktop, disconnect any peripherals other than keyboard and mouse, disable antivirus, if any and run Repair Permissions.

When completed double click the update and let it run until it restarts the computer. There may be two, or even more chimes, and rebooting may well take five minutes or os - just let it run its course.

Connect everything back up, run Repair Permissions again and there you are.