If the airway is blocked the motor will run faster and there will be no cooling air so it will get hot - it might be this that's causing your problem but it's more probably the motor brushes begining to fail.
If you follow Pete's advice don't leave the machine unattended - stay around for emergencies.
Henry I may have to be replaced by Henry II...
If you can dismantle him you might be able to inspect and even replace the motor brushes but the rotating part of the motor that the brushes rest against; the commutator, may be damaged.
Peccavi, September 2009
