You probably have been for ages, it's just that nothing was checking them until you enabled the EDAC module. Note that your system may be experiencing data corruption, so you should really check this out.
- Your PCI device is broken by design, and reports parity errors, when none occur (if you get pretty sure that this is the case, then please add it to the list of PCIDevicesWithBrokenParityDetection)
- Your PCI device is faulty (Please add it below)
- Your Motherboard is faulty (try moving device to another PCI slot)
- Your system may have PCIPopulationRules that you haven't followed
- Rule out PCIMechanicalStress
- Bad connection caused by dirty connectors - see HowToCleanEdgeConnectors
- Your power supply is faulty/underspeced
- The electrical supply is faulty (e.g. transient spikes / droops)
- Other electrical noise (either from inside, or outside the system) is causing the problems
Please expand on this and add links!
 Devices which are known to cause Genuine PCI Parity Errors
- SuperMicro H8DAR-E motherboards - see mailing list archives (FIXME - which revisions?)