I am just reposting my response to a similar question because I never found a solution to this problem just a work-around. I would love to know the actual solution.
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I have encountered this issue as well. I never solved the issue but did find a work-around. Unfortunately, this temporary solution may not work for more 'heavy' users then I. Although, many have commented that this issue happens even on small projects (as it did with me also), many usually create much bigger projects and are using the smaller projects just as a litmus test. I qualify this because the work-around I discovered is using USB 2.0 to connect my external HDD rather than either of the firewire ports on the drive. So, for those wanting to create larger projects, this solution may not be an option. I won't delve into the details here, but I will include a link to my thread so you can see all the troubleshooting I did and the suggestions that were offered.
http://discussions.apple.com/thread.jspa?threadID=2102925&tstart=0
Or, you can search the forums for error 10010.
The only other items of note I can think to add at this point is I am still on 10.5.8 not SL. Logic 9.1.1, and I recently increased the amount of RAM to 4G. The work-around has been working for me, and I haven't had time to check that any of these updates fixed the problem. But I will soon and will report any changes.
I hope this provides some insight.
Chris