If it's an intermittent problem, have you considered that either the drive or power supply might be starting to fail? Possible for you to check voltages, or to remove the extra controller and run a drive directly off your accelerator? Have you tried it with any other expansion cards removed, and making sure all your connectors are nice & clean?
Personally I had pretty bad luck running a drive off a separate controller than my accelerator, and this was even using both devices by the same manufacturer (a GVP accelerator and a GVP HC8+ controller). Would recommend if possible just putting a drive on your accelerator and running like that. Good luck!
