Worn door locks (tumblers) can cause the lock not to work. Removing the lock and replacing the worn parts (tumblers) is needed to get the lock working again.Google+
Car Problem Reports
Honda Civic Door Lock May be Sticky and Not Work Due to Worn Door Lock Tumblers
Honda Civic Problem
Average Mileage: 96,333 mi (36,000 mi - 130,000 mi)
Visitor, 2009 Honda Civic, 36,000 mi
Driver's side door won't allow the key all the way in and will not turn. Tried WD-40 and also some graphite. I loosened up a bit, but still can't get the key to work. I called the local dealership and they advised using my second key or the valet key. The primary key shows no sign of wear and works fine in the passenger door lock. Should have gone keyless!!!
Visitor, 2004 Honda Civic, 87,000 mi
Same issue with lock. THis will be second time to replace it. Never had this happen with any other car I owned.
my driver side door does not unlock with key. i'm not sure if this is the same problem but it sounds similar
Visitor, 2004 Honda Civic, 130,000 mi
havent gotten it fixed yet, just stopped working yesterday.
Visitor, 2004 Honda Civic, 90,000 mi
Three of the five timbers have quit working
Visitor, 2004 Honda Civic, 125,000 mi
Driver's side door lock stopped working at about 80000 miles. Tumbler had to be replaced.