:Update: 6/1/2016 this is Now fixed as of PVS 7.9 – adding machines to a catalog as large as 3750 now functions as expected.
There was a bug “recently” fixed in 7.6 where you could not create a machine catalog of more than 999 devices. However, that limit seems to have a similar bug that still remains in 7.8 I was able to successfully create a catalog with 1250 machines but not able to create one with 2500 machines. I did not test anything in between. However, I wanted to highlight out the discussion thread I created on the XenDesktop forum that has a script that will allow a manual workaround. Click to read on!