Phone your supplier and see if you've just been uprated to 2MB for free. Have aseen a lot of this.
Its normally down to line problems. Having the Sync light flashng means that the connection was lost and that the modem is trying to reestablish it. If the weather is particulary bad round your neck of the woods and you have overhead lines that might be why, pick up the phone and listen for clicks and crackles.
Also make sure everything has a microfilter on and unplug any extentions you have to see if that helps.
Ric