Problem
When using LabSim, some text areas randomly appear and disappear. Sometimes highlighting or clicking can make them reappear temporarily.
Solution
This is generally caused by Internet Explorer. There are 2 steps to take in IE that will fix this issue:
1) Enable compatibility view. Go to www.testout.com and click the compatibility view icon (the icon between search and refresh in the address bar. It looks like this: 
2) Add "*.testout.com" to trusted sites. To do this, go to tools>internet options>security>trusted sites, then click the sites button. Uncheck the require server verification (https:) checkbox, then type *.testout.com and click add then close. Your window should look like this:
Additional Comments
Another option is to use a different browser like Chrome or Firefox.