I have an Alcatel DECT phone which worked perfectly before I was ADSL enabled.
The phone detects if the line is active and prevents you using the line if it is. (i.e. if someone is on the phone upstairs you can't dial out). It indicates this by a flashing light on the base unit and a flashing 'off hook' symbol on the handset.
Since going over to ADSL, it now sometimes indicates that the line is active even when no other phones are off hook. Annoying because you can't then pick it up to dial or answer.
Doesn't always do it, appears to be fairly random.
Rang Alcatel technical who bounced me to their repair agent who bounced me back to technical... :-(
Has anyone seen anything similar?
PS. All filters installed properly, can reproduce with a single filter plugged into the BT socket + Speedtouch USB modem...
I don't know if you've had your problem resolved yet, but 'm hoping that perhaps I can shed a little light on your problem.
Your Alcatel DECT phone is obviously detecting a signal on the line, that's why it won't let you dial out. My first try would be to try a different microfilter - they are not expensive (try www.solwise.co.uk). Alternatlvely, a perhaps wrap your phone lead that goes to your Alcatel through a "ferrite core" (see www.maplin.co.uk) which will get rid of any RF interference that's disturbing your phone. (you can cheat by wrapping your lead round a six inch nail too!!!)