Asus Transformer slow charge
Charging via USB can happen at very different rates depending on what the "host" end is plugged into.  Generally the vendor-supplied wall charger is the "fastest" way, but perhaps something has gone bad with your supplied wall adapter.  You should be able to improve charging times by shutting off wifi, GPS, etc, and making sure the screen is off.

See these questions for more details on what to look for on your adapters:


Why is charging from computer using USB slower than using an outlet?
Galaxy Tab is not being charged through USB Cable