If you want to know FOR A FACT whether anything with legal ramifications is true, you need to interview several lawyers who have tried a case involving same and see what they say. Of course, you will need to pay full fees involved.

If you would like to know with less certainty than that, consider the following.

Thousands of users have flashed their devices and not one has ever reported problems with Nokia care or reported here that anyone from Nokia has ever told them that flashing voided their warranty.

Overclocking is a separate issue, and there have been specific warnings from Nokia that overclocking voids the warranty. I have not seen any written claims from users that state that Nokia has told them their problem won't be fixed becaused they overclocked, but it could happen, in theory.