What operating system are you running and what service pack? Are the idle time quick scans running? What programs cause Norton hanging to hang. Do you use programs that handle compressed files? Have you tried turning compressed file scanning off (under computer
settings)?. Also do you have NIS or NAV and what is your version under Help & Support>about?
Is that Adobe Dreamweaver CS4? Would indicate a fairly new version. NIS2005 is using an antiquated engine compared with
NIS2009. Old software often doesn't run well with new. You don't have idle scans or pulse updates on 2005 which use much less of your system resources and update faster providing better protection.
There may still be some workarounds with Dreamweaver, and we will wait for Phil_D to comment as he uses that software as well and will have a better idea how to help you.
You do not have to change any compatibility modes for Dreamweaver 8. You would only need to do that if Dreamweaver were not performing correctly with your current operating system.
I agree with delphinium that when possible you should upgrade to NIS 2009.
However, you can try this to rule out any malware issues:
1) Be sure your NIS 2005 has all the current definitions and run a scan in SAFE MODE.
2) You should also try running the Norton Online Security Scan. Select the button on the RIGHT "Continue to Symantec Security Check" and in the new window select "Virus Detection" and let the scan run.