Upgrading from Parallels Desktop 5 to 6 caused DNS query resolution "slowness" at Mac OS X level
Start by making some tests in your Terminal:


Use nslookup and try to lookup certain stuff (www.google.com, www.ibm.com, etc) See how it works from there.
Use ‘dig’ (another command) to do the same. Dig will be much more verbose and will show you more information about the Lookup per se.
Make sure your DNSs are correct in /etc/resolv.conf (try google’s 8.8.8.8 if unsure).
Check your Console for possible messages related to Network adapters or loops going on.


Edit: It all seems “normal”. Do you use Shared networking? Can you try disabling vnic0 and vnic1 (those are the parallels ones). I recall having slowness problems (back in parallels 3.x) which I fixed by using Bridged Networking instead of shared. I didn’t think the issue was still an issue a few years later!