525 is a bit flakey when you try to download on that initial time to setup the input and output tables. So if you repeatedly tried to download that first time, I have found if i reset the drive to factory defaults. That initial download will take. Yea i know you have to reprogram that IP, but its the only way that works.
But make sure you have it on RSLinx before you download with your program configuration.
Also, IO config tree for 525 is really flakey for L61 and L71 and sometimes for earlier CompactLogix plcs. So if it does not work on the IO config tree is to use CCW (connected components workbench). CCW will work where IO config tree goes south.