Guys to check if there is a cable problem try going to www.pingtest.net and do a ping test. Click on Begin test and let it choose a good server automatically. check your packet loss, if high then cable issue.

Then to check your download and upload speed go to www.speedtest.qa.
I had some problems with mine, then changed the router and also found out my connection was downgraded from 4mb to 1mb and took them 2 weeks to fix that, but its all good now.