error 678

Hello everybody! Nice to be here! (This is the first time I posted a question, my first time in this site actually!) I would really appreciate if anyone could really explain to me what happens to the computer when the error 678 error ocurrs. Being a tech support that I am, when I'm still doing DSL calls, all I do is have anyone with that error do several stuff when the members connection is enabled, like clearing temporary int files, forcing DNS, disabling firewall/ anti-virus....and if the same error occurs I transferred the call to our Tier 2, and nobody really able to give me a clear and definite explanation on that.