I had such a problem with printf too,
it seems to be a problem with printf, but printf uses a
lot of resources (about 1700 byte of stack) and
simply produced another error earlier.
the stack was sometimes destroyed, i searched one week,
it was a problem with 16 bit SRAM timing. I had to setup
one setup cycle for sram, otherwise sometimes the sram was writing
to illegal address location too.
(address signals not stable at write pulse).
I ran into this error because on the cyclone dev. board the sram uses
zero setup time.
