I'v just started using Courselab so there is probably a simple answer to this one.
The text is not showing in the text boxes on the actual slide. although I can see it in the thumbnail on the left and when I double click on the text box, it displays in the text editor. The text is black and the background is white so it's not caused by the text colour. Strange thing is that every now and then it does actually display OK, on loading the lesson.
The text does display when I view the module.
Has anyone else experienced this problem?

As Vyacheslav points out uou will find that if you copy and paste text directly from something like MS Word or from a web page you often get a lot of formatting code copied over.
If this is referring to a formatting scheme such as CSS in web documents then you may get problems. Pages that don't use CSS can be a real problem.
With MS Word you'll have lots of code attached to the text that can give you problems.
For both of these manually editing the text in html mode is the ultimate answer but a little lonf winded.
You can cut and paste into notepad which will remove all of this extraneous code and add your own formatting in Courselab.
I tend to use this method or process text in Open Office Write which is much cleaner.

Hi, Bob,

Perhaps there are some HTML-tags, that make this text invisible. Please try to open this text in HTML mode (using the button in Text editor - second row, right button) and look at the text. Perhaps there are a lot of "garbage" from Word? You can use "eraser" button to clean some Word garbage.