It's not the regulator, the window just needs oiling. You need to put some upwards pressure on it, and it'll roll up slowly. Also while putting upwards pressure on it, pull it forward towards the engine to relieve the stress.
The weather stripping that guides the window up becomes very dry and hinders the window from rolling up. You also might notice it has more of a harder time rolling up after it rains.
My drivers side has been doing this for a while now, and I just keep oilling it. Just don't ever put it all the way down, so you have some of the window sticking out to grap onto and pull upwards.