While I only work in the 64bit version of Max, I sometimes like to use the Advanced settings in Backburner to Send Job As: 32bit so that I can take advantage of the whole farm when I don't need a lot of RAM.
A problem comes when we have plugins that are named differently for each OS flavor. i.e. Plugin_64_2009.dlt and Plugin_32_2009.dlt.
When I send a job from 64bit but send it as a 32bit job, the tasks fail when the 32bit machines can't find the plugin named Plugin_64. There isn't a problem with plugins that have identical names for both flavors of windows.