ATtiny serial.print() crash with INTs
It is much better to store string literals in the FLASH only. In Arduino there is __FlashStringHelper class and F() macro ensures that correct version of print method is used and that the string literal is not copied into the ram before it's printed.

Basically if you don't have enough memory, using lots of string literals results in stack overflows, coruption and/or returning to random adresses and it looks like crashes/resets.