How to Identify faulty bus pins on LCD?
If you suspect shorted or broken wires, you may use test patterns. For AVR, most usable is to first set all pins to pullup (but not drive) and then drive low every pin one by one (0HHHHHHH -> H0HHHHHH -> HH0HHHHH...). When drive some pin, monitor other pins for change of level. With this you'll be able to find signal-to-signal and signal-to ground shorts. Also, if you test signals on LCD side with multimeter, you'll be able to find shorts to Vdd and breaks.

Also, don't you think your problem might be with some error in initialisation sequence and its timings? In my experience there are most problems with LCD. E.g. LCD need delays after some of initialisation commands, also contrroller mey need to keep relation beween some parameters (mostly row timing vs row length)