Below is the defect you're probably thinking of. The engineering special fix was superseded by 4.0(2)sr1a and now sr2. Also, the symptoms do not match that of your problem.
http://www.cisco.com/cgi-bin/Support/Bugtool/onebug.pl?bugid=CSCef49861
If you are hearing dialtone, there's either a very strange defect (unlikely) or a route pattern you don't know about (far more likely). From CCMAdmin, go to the Route Plan menu and then to the Route Plan Report screen. Show all patterns that begin with 7. It's also possible you have a loose wildcard pattern you might not see right away, such as XXX or [A-B]XX or similar that could be picking up the call.
If you can't spot an errant pattern yourself, you can give the Dialed Number Analyzer service a shot (search cisco.com for documentation). If you don't want to install it or aren't sure how to use it, you can post a dump of your dial plan here and we might be able to spot a problem pattern for you. From the Route Plan Report screen, you should see a 'View in File' link in the upper right corner. Click on that and your browser will download a file called 'Numplan.csv'. Reply to this message on the forum and attach that file to your message. It would also be useful to know if the dialtone you hear is CallManager outside dialtone, which is the higher-pitched dialtone you hear when using a route pattern with 'Outside Dialtone' checked, or regular dialtone, like you hear when you first go offhook.
