Problems lists problematic (ill-formed) environments you have created in Environments.
If you create an environment that is not well-formed, Language Explorer will copy it into Problems and generate an error report that explains what the problem is. This is important because problematic environments are not available for selection in the various dialog boxes that list environments or available to parsers.
Once you have fixed the problem, the environment is automatically removed from Problems.
The Problems Help topics are the following:
View problems with environment