When I mentioned that comcast dns servers do ICMP rate limiting, that means that they may not respond to ping requests and may also show timeout blips on traceroutes.
again, try using dig or nslookup to verify if you are having DNS issues.
traceroute and ping blips to 75.75.75.75 or 75.75.76.76 prove absolutely nothing due to their ICMP rate limiting. I will get the same "packet loss" that you do and I can guarantee you that my internet connection is having zero issues.
Edit: In case anyone was wondering what a typical dig response at 75.75.75.75 would look like:
ryan@skynet:~$ dig @75.75.75.75 google.com
; <<>> DiG 9.8.1-P1 <<>> @75.75.75.75 google.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 10620
;; flags: qr rd ra; QUERY: 1, ANSWER: 11, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;google.com. IN A
;; ANSWER SECTION:
google.com. 211 IN A 74.125.224.39
google.com. 211 IN A 74.125.224.37
google.com. 211 IN A 74.125.224.32
google.com. 211 IN A 74.125.224.34
google.com. 211 IN A 74.125.224.33
google.com. 211 IN A 74.125.224.46
google.com. 211 IN A 74.125.224.41
google.com. 211 IN A 74.125.224.36
google.com. 211 IN A 74.125.224.40
google.com. 211 IN A 74.125.224.35
google.com. 211 IN A 74.125.224.38
;; Query time: 19 msec
;; SERVER: 75.75.75.75#53(75.75.75.75)
;; WHEN: Tue Jan 22 17:16:18 2013
;; MSG SIZE rcvd: 204
and here's a nslookup against 75.75.75.75:
ryan@skynet:~$ nslookup google.com 75.75.75.75
Server: 75.75.75.75
Address: 75.75.75.75#53
Non-authoritative answer:
Name: google.com
Address: 74.125.224.39
Name: google.com
Address: 74.125.224.37
Name: google.com
Address: 74.125.224.32
Name: google.com
Address: 74.125.224.34
Name: google.com
Address: 74.125.224.33
Name: google.com
Address: 74.125.224.46
Name: google.com
Address: 74.125.224.41
Name: google.com
Address: 74.125.224.36
Name: google.com
Address: 74.125.224.40
Name: google.com
Address: 74.125.224.35
Name: google.com
Address: 74.125.224.38