Since you have posted this request under the Slingbox PRO and Slingbox software Updates, it is necessary to let you know that the latest firmware version for the Slingbox PRO is 1.4.20. The firmware version 2.1.64 is for the Slingbox PRO HD.
If you want to know how to update the Slingbox firmware version, feel free to check this link.
Finally, keep in mind that the SlingPlayer Mobile application for iPad is officially supported only if you have the Slingbox SOLO or the Slingbox PRO HD. It will not work if you have a legacy Slingbox model (Slingbox PRO, Slingbox AV, Slingbox TUNER or Slingbox Classic).