I would make sure that you have the same visions of the MXF codec on both machines. I suspect that this is the source of your problem. You also need to make sure that there is not a network path issue or some other network slowdown. To check that collect the files and then physically move them to the second machine.
Thanks for the input, Rick! All of the assets are actually in the same location on an external hard drive, so I don't think there should be a path issue. However, how does one check to see if they have the same visions of the MXF codec? Thanks again for the help!
You could try to remove/rename the mxf files temporarily to see if they are causing this or if there's any other issue. If the projects opens (obviously with "missing footage" error messages, save your project under an new name and try to relink the missing footage. In the worst case you might actually get an error message. Another approach would be to transcode your mxf files to another production codec/format on your CS5 version and see if that's working on CS5.5.