Assuming you mean the sleep/wake button(on top),
Try doing a hard reset: Press and hold both the Home button and the Sleep/wake button simultaneously for about 15 seconds and release when the Apple logo appears. Maybe this is what you meant by a soft reset.
If that doesn't solve the issue, you could also try backing up the device and restoring the device as new.
In that case, follow the steps in: http://support.apple.com/kb/HT4137
NB: set up as a NEW device because a software issue will be in the backup. If the issue persists after restoring as new, you should offer the device for service.
If you're not able to restore the device, this one might help: http://support.apple.com/kb/HT1808
Using his article will erase everything on the device, so make sure you have a backup!
Your iPhone seems to have several bad issues going on. The Lock Button is most likely damaged at the internal portion of the switch, there is a small plastic piece the size of this ( * ) that has most likely moved slightly or come loose. If there is Warranty or AppleCare this will be covered, make Genius resevation or set up service and take or send to Apple for resolution.
Since I'm the opposite of a genius, an idiot, without insurance, what would the aforementioned service cost? I will attempt to restore the phone as well, but given the fact the lock button performed a slow death this morning, going from workign fine to working sometimes to freezing and now simply not working at all, it seems like a hardware problem. :/
With Apple this is handled with Replacement iPhone 4S, cost is $199. You can try Virtual Lock Button. Settings App > General > Accessibility > Assistive Touch > ON > tap new white screen button > Device > Lock Screen. This can even be used to turn iPhone OFF. To turn ON connect to power, charger or USB of computer.