I had been receiving this error lately sometimes when running QB 2009. I run QB in a Windows XP VM on my Mac. The first thing I did to address the problem was to free up disk space since I figured the erorr might have something to do with running out of virtual memory in Windows. After seeing that my disk space in the VM was low, I made enough room to give myself about 3.5 GB disk space free. This seemed to fix the problem for a while, but then it came back again. I thought it might be the VM so I moved QB to another XP VM, but immediately encountered the same problem.
I checked Google for some answers and found a KB article on Intuit’s QB site discussing the problem. It talked about low resources, problems with QB update, etc. Then I saw mention of checking firewall, AV software (the usual suspects) and considered excluding the QB folder (which also contains my QB files) from AV scanning. So far this seems to have fixed the problem. One of the QB files seemed to have this error more than others (probably because it’s larger and took more time to scan). So my advice if you are having data access problems is to exclude the folder from AV scanning and see if that helps. I have heard of doing this before with other database programs’ data as well.