MacOS – “Not enough space” on partitioning

disk-utilityhard drivemacospartition

I have a 320GB harddrive with 95GB free. I boot to a 10.5 disk, open disk utility, and add a 40GB partition. Halfway through the progress bar, though, it tells me that there's not enough space. I'm not sure what it means- I'm just splitting my free space off to another partition- it shouldn't need any extra space.

Any ideas as to how I can partition my drive?

Clarification: this is my laptop's internal drive- the one I boot from. I can't boot normally and partition with /Applications/Utilities/Disk Utility.app.

Best Answer

Ok, solution found on an old superuser question, posting here for posterity.

I just needed to defrag the thing

I got Coriolis iDefrag. I ran that on the compact setting (required restarting into it's own special mode, but no disk burning was needed). A few hours later I tried to resize the partition and it worked fine.