I've been experiencing intermittent loss of sync for some time and have recently changed from a PCI ADSL modem to an ADSL Modem/Router with 4 LAN ports (ACEEX AR41) which did not alleviate the problem but allows me to monitor the times of loss of sync.
The synch is lost in a regular pattern. Today, so far is like this -
So about every 85 minutes sync is lost, a couple of reconnects last for a few minutes each and then the cycle repeats. This pattern was not evident on Easter Sunday when I had a continuous connection for over 18 hours.
There can be up to 5 computers on the LAN including one using a VPN but the symptoms are the same with only one computer connected.
I have filters on all used telephone points and I've tried changing the filter used by the modem. There is no modem noise on the telephone line. The modem is not connected to the master socket but I've checked all the extension wiring. The house is about 4 years old and the wiring was done when the house was built.