I installed today Magento 126.96.36.199 together with a Theme I bought. They offering a Quick-Installation where you copy the complete Magento Directory including the first Theme configuration (I was never sure that's a good Idea, but for Configuration it's much easier).
The Installation then comes in Magento 188.8.131.52 and I tried to upgrade via Magento Connect.
But if I click "Check on Upgrades" nothing happens, except, that "Check for Upgrades" disappears.
What do I have to do?
I will recommend you to check console for real error. And also check in system.log or exception.log file for error and try to solve it.