I never seen this problem before. Have you try to change the TV Input Types or give a try with another TV ?
Maybe you can try to empty the cache manually and see if this resolved your problem.
As you can see in my screen shoot, everything work nicely for me with same version of MODX.
Yes. In my screenshot, the top TV type is a plain text box and the bottom two are Rich Text. I cleared my cache too. No dice. Thanks for your ideas.
discuss.answer
Big thanks to Ryan Thrash (MODX Support) who said
"Ace actually has a problem with TVs and creating small text boxes in 2.5.1 iirc." I had no default RTE, so I installed TinyMCE-rte which solved it! Woot!!!