If you are paying for the enhanced rate your line was likely provisioned at 1792 which would leave around 1.5 (1500) after overhead. You are only getting 768 now and thats before overhead. I suspect line noise issues causing sync loss . The modem will then train down to a speed it can support. Take a phone press a button and listen for noise / static / or crackling on the line. If your getting a lot of noise you can call in voice repair don't say nothing about the DSL correcting the noise will take care of the DSL sync issues. If you see the dSL light going red or flashing (depending on modem model) that's most likely a line issue / loosing sync .