'Apple Imac ( 1 yr old)' - this could translate to an iMac Intel with either a 1.83 or 2.0 GHz Core Duo microprocessor, with MacOS X 10.4.4 - as the initial installaton.
Is the above hardware and installed MacOS X version (assumed) correct? If not, please provide (in detail).
Have you since, its purchase, installed any form of 'Security Update(s)' and / or system (MacOSX) updates? Either via the 'Apple, Software Update...' menu item, and / or 'System Preferneces' 'Software Update' utility, of the '/Applications/' folder); and / or the '
Apple Downloads' web page?
If so, what upates have you installed?
Also, if so - had you performed a 'Disk Repair' and 'Permissions Repair' (via 'Disk Utility', in the '/Applications/Utilities/' folder) prior to the update(s) installation(s), and a 'Permissions Repair' after the update(s) installation(s)? The latter is a standard practice (with the now Windoze like MacOS).
'... could Norton Firewall be responsible?' - possibly. There are numerous system related problems due to any number of Apple and / or third party software installations.
The version of 'Norton Firewall' was not provided.
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By 'System freezing up' - are you referring to a 'Finder' action (such as in the copying, deleting, duplicating, folder creation, moving, item [file or folder] name editing , etc.) or similar freeze? (typically, indicated by the 'Steve Jobs' / Apple 'Spinning [beach] ball from hell' animated [Windoze colored trademark inspired] mouse cursor), or - a no matter what application is currently the front most process, at random, user interaction process no longer posssible type of 'System freeze'?
