This is the usual signs of an overcharged prommie...... that is what the plinking sound is. When there is too much refridgerant in the prommie, it runs back down the hose back into the compressor... the reason you get a plinking sound is because the oil in the compressor is VERY warm, and the refridgerant is VERY Cold.... like when you drop a drop of water into a pan of boiling oil (not recommended

)
This is why you get the build up of ice also... as this is where the refridgerant is flowing back to.... so like it would in the head... as soon as it reaches somewhere insulated... you get ice.
Now unfortunately quiet a lot of units left Chip-Con (nVentiv) like this, but there is a way around to keep the problem at bay, not solve it.
If your whack your CPU volts up as high as you can and keep the CPU at reasonably high load all the time, the refridgerant is evaporated a lot quicker in the head, therefore not giving it the change to run back into the compressor.
The only way to solve it completely, is to hand the unit to someone such as Marci (he's registered here somewhere

) and he can extract the refridgerant for you completely and regas it, or let out just enough refridgerant to keep the problem at bay.
Hope this helps