Giro,
For greatest ease, I would looking installing a demo of NetSight, pull in all the switches you can, and then test for loops as above mentioned. The X460 (if they are not G2 models) may not be fully compatible with all the features of NetSight, but I'm sure that they and the Allied switches (if they are managed switches) will have some compatibility. Also, if you can add the MiBs for the Allied switches if they are available, that may enhance your experience.
A short non-authoritative test for loops with the C5K would be to check the CPU utilization. If it's high, likely there is a loop or some other issue.