I had this issue this morning. I think the problem happened because the launcher suddenly decided my launchpad.ini needed to be updated. Here's the excerpt from the ".DownloadInfo.txt" file:
**** Starting at Sun Feb 26 11:14:08 2012 with plug-in 1.0.3.170 ****0aec-00:00:00:Checking game installation...0aec-00:00:00:Found 2 file(s) to update.066c-00:00:01:Replacing eq2_default.ini07a4-00:00:01:Replacing LaunchPad.iniFinished downloading 860 bytes in 0.180 seconds (4,777 bytes per second)0aec-00:00:01:Beginning asset preload...
After I downloaded the full client and did a "new install" over my old EQ2 directory, the preloading went away.