you definately have a dialPlan/DN stepping on routePattern issue.
if you are using CCM 4.1x + you can use the ccmAdmin>routePlan>routePlanReport menu item to find any DNs that may be stepping on the routePattern in question; as previously mentioned.
if you have CCM 3.x you must go through all routePatterns and DNs manually to verify they are not stepping on each other.
example, if you have a routePattern 91xxxxxxxxxx that is to provide outside dial tone; you may also have a DN for example, 9200.
(the 9200 DN will not provide dial tone and is stepping on the 91xxxxxxxxxx routePattern that is to provide dial tone; this type of issue must be corrected to get your dial tone back to normal)
(basically, in the example above, CCM knows there are more potential matches for the dialed string of "9" so it does not provide the tone as the routePattern specifies until it knows it is to use that routePattern for sure, as when you then press the "1". now CCM knows it is to use the routePattern in question and provides the dial tone at that point)
please see the following link for troubleshooting dial pattern problems:
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