PCI Parity Error on system startup

When booting 1st thing in morning- Dell Pentium III Win98 (nothing changed) i get BSOD – “system error -Memory parity error detected -system halted”. When i hit off buttom or restart, the black screen comes up and quickly displays five lines of typeall saying “PCI Parity Error on Bus/Device Function 008h”. When computer reboots it does so in Safe mode or Normal ok. and computer runs fine for the rest of the day. Is this telling me a ROM Chip is going bad or what?