I was pulling my hairs out over unexplainable crashes yesterday, occuring on a Motoruino board.
It occured after simply enabling some more debugging stuff and it started to act all weird: crashing randomly and corrupted serial data.
It really had me going nuts at some point -- even wondering if the chip was bad. All until I read some interesting stuff about the .bss and .data size having limits. A shame that the Arduino IDE does not check for the allowed sizes for SRAM.
The following command can easily reveal my problem: