Norton AV is not compatible with Apple OS X - you need to get rid of it.
Norton Antivirus has a very long and illustrious reputation for mangling Mac OS X systems, sometimes to the point where a complete reinstall is necessary. Among other things, it installs kernel extensions which are known to cause kernel panics and system freezes; it contains known and documented bugs which can silently corrupt Adobe Photoshop and Adobe InDesign files, destroy a user's ability to authenticate as an administrator, and (on PPC systems) can cause Classic to stop functioning; and Symantec has on at least two occasions now released flawed .dat file updates which erroneously report certain critical Mac OS X files as "viruses." (Deleting these "viruses" causes damage to the system that in some cases renders it unbootable.)
As for the DNS issue, try using Open DNS:
Adding Open DNS codes to your Network Preferences, should give good results in terms of speed-up as well as added security:
[b]If you are using a single computer:[/b] Open System Preferences/Network. Double click on your connection type, or select it in the drop-down menu, and in the box marked 'DNS Servers' add the following two numbers:
208.67.222.222
208.67.220.220
(You can also enter them if you click on Advanced and then DNS)
Message was edited by: Klaus1
