The local ISP routers at hop #3 (before the border routers) are constantly switching to other routers 209.88.128.129 -to- ....137 -to- ....145 -to- ....153. There is a persistent PL and errors at hop #3, whereas the hop #4 has very minimal PL and errors. Why would there be such a high number of PL and errors at hop #3?

Also interestingly to note is that hops 5 through 18 recently have been experiencing a very high number of PL and errors as well. In the past this has been very clean (low PL and errors)

"VoIP" is our main application, and with these type of errors and PL, the VoIP quality becomes unacceptable. Can any one please give me your expert opininion of what may be happening?

Does the increasing spyware and adaware phenomena have any effect on this problem?