The airport is large; you can find a map at www.fly2houston.com (click on Bush Intercontinental IAH) but 50 minutes should be fine if everything is ontime or close to on time.

You will not need to reclear security and your flights should stay within terminals C and E, which you can walk between. There is also an elevated train from C to E past security (seperate from the underground train pre-security) however depending on your gates walking to the train could take just as long as walking between the terminals.

There is a map in the Continental magazine that is helpful and has the gate numbers.

Good luck.

Ciao,
FH