Hi, after upgrading to ICS- my Google Play app update downloads are brutally slow. In fact, not a single app has downloaded successfully. I cleared data and reverted to Market- but am still having the same problem.
It sounds as if you uninstalled the Play app in favor of reverting to the Market app. It should then office you the Play app again. You may want to go to settings - apps - all and find the Market app and tell it to clear cache and settings, then force stop/close and restart your tablet. I'm not certain the old Market app would still work correctly.