Asterisk T1 Channel Limit

I have been using Asterisk 1.4.18 in production now for 11 months without any issues. That is until about 10 days ago. Now it will randomly drop calls. I have replaced my T1 card (T410P) and changed my zaptel.conf to make my provider the clock source and it still drops. I get this error in my message file:
Timeout, but no rule ‘t’ in context ‘default’

It seems that is the only message Asterisk throws. I am using 1 voice T1 with 23 ports and a PRI. My question is that I have about 120 phones running on this box and only 23 incoming/outgoing channels. How would I find out if I am reaching my channel limit on my T1? Is there anyway in Asterisk to see? Is this an error that Asterisk would throw because of a limit being reached? Any help or direction would be appreciated.