I ran across this issue when a customer called in about it. The alterations that Altiris does to the MBR interfere with using the Ghost client on that machine afterwards.
It creates an error message: "Error 15210: NTFS signature, should not be FAT32".
What we found to resolve the issue was to reinitialize the MBR through use of GDISK or FIXMBR.
Created document number 2008091609500360: "Error 15210: NTFS signature, should not be FAT32" occurs when using Ghost on a machine that previously had an Altiris image deployed to it.
In that kb article, I attached (in the Internal Notes section) a link to a legal case between ALtiris and Symantec (when they were different entities) wherein the alteration to the MBR by Altiris is described. Altiris-side people may already be aware of this, but this was new to me.