Mine too! Happened last night. Got home from work late, went to unlock my phone to check my messages / e-mail and the lock button snapped clean off. I've only had the handset four months.
For the info of you all, I have to concur that Pocket Lock (available free from Ovi Store) is excellent and certainly easier that the fiddly lock switch. That said, you ALL have the right to have your handsets repaired free of charge (so long as the lock button was not broken as the result of deliberate misuse).
Your handset is covered by the Sale of Goods Act, 1979 (which decrees that an item should be fit for the purpose for which it was purchased) and the Consumer Protection Act, 1987 (which makes manufacturers liable for design faults in their products.)
Clearly there is a problem with the design of the lock switch. It's smaller and more fragile than on previous models. I fixed mine by putting a small amount of glue on the protruding nodule and inserting in back in to the body of the phone but I don't expect my repair to last.
So for those of you who want your handsets repaired and who experience resistance or apathy from O2, Nokia or anybody else you simply need to remind them of their responsibilities under the above legislation. You'll be surprised how helpful they become!
PS - The X6 is a new handset. The key here is what most people would consider a reasonable period after which a fault could develop. I firmly believe it is unreasonable that any X6 develops this fault until it's at least two years old.
Amazing, it works!!! Thank you :-) I was just about to take my phone to O2 for repair but decided to check this forum first. Now that I've got it unlocked I can get all my contacts etc out of the phone - O2 said they would delete everything in the phone before repairing it., I'll also check out the "phone unlock" app that another poster suggested.
I had the same problem with my X6 yesterday noticing the buttong had fallen off leaving my phone in a permanent locked state - After a row with O2 who wanted to charge me for the fix (and finding a shop to take it back to and waiting 7 days etc etc) I gave up. Upon finding this forum can I say I feel slightly better knowing I am not the only person to have suffered with this but also a MASSIVE THANKYOU to the person who suggested plugging in headphones - it worked a treat and now I have my phone back again albeit I cant lock the screen. Thanks again its gems like this that help us all.