I had the same problem with my 4s since the last update,intermittent sound(mainly no sound),no bars on the ringer logo,no clicks when typing messages etc,it was driving me crazy.I tried cleaning the dock and headphone socket with a tooth brush but nothing helped.
I made an appointment with the Genius bar,told him that this problem just appeared since the last update.The guy told me it was a dock problem.The morning i visited Apple shop the sound was fine,after being off all the previous days,typical! Basically the phone thinks it's in a docking station(docking speaker etc).He claimed it was dust on the connectors and cleaned it with a brush,although he admitted mine's was spotless! If the problem persisted i was to try a full reset or return and the option was a replacement phone at £140 as my phone is now 14 months old.
The problem re-appeared within hours of leaving the Genius Bar.I went home backed up iphone to pc and did a full reset,nothing changed.
I searched the internet and found this thread and many others and decided i was going to try and replace the dock connector myself.
I ordered the part from ebay,many sell the part for as little as £6 upwards,i ordered mine from a seller who claimed it was a genuine Apple part for £10.I also bought the screwdrivers to open the phone,they cost just £2.
I followed a guide showing you a step by step guide of how to replace the dock and mic(they are connected) and the upshot is my phone is now working perfectly again.I'm glad all my sounds,clicks and beeps have returned!
It took me just over 1 hour to do it,a steady hand and patience.
It is definately a hardware problem!