When you import a Netboot image to use with Mac imaging, we would create empty packages in the package server. The source of the problem is a result of IA64 options not being completely removed. Having too many empty packages results in poor performance from the package server, and possibly a lot of extra time to download other packages.
This is a known issue.
To fix this issue we need to install the Cumulative pointfix for 7.6 HF7. TECH234364