Isopropyl alcohol has water in it. DA does not. You can get DA cheaply by the quart in a steel can in the paint supply section of many hardware stores and wal-mart. Water on internal engine components causes rust/corrosion very quickly due to the fact that all the exposed surfaces do not have a coating, so it's raw metal. The alcohol in isopropyl washes away any oil and leaves behind a trace of water to cause rust/corrosion when it dries.
You said you "cleaned" the bearing, but you didn't take it apart? How did you clean it? What engine is it specifically? Is the bearing on the outside of the back plate or the inside? What fuel are you using?
Running a high oil content fuel can cause excess oil buildup in the OWB causing it to gum up and slip more frequently. Especially on engines that run an internal OWB. Also, if it's an internal OWB, you need to make sure to run the engine completely out of fuel before storing it for any length of time. The methanol/nitro in the fuel in the crank case evaporates, but the oil does not. So when the fuel evaporates, it leaves behind a sticky coating of castor/synthetic oil.
