Ok . . . first
Basially - I need to know more information about your problem besides the text disapears while I am typing and then reapears after I click out of my typing area. Chances are that those colors on your PC are too similar and therefore do not show up well while you are typing.
Make sure that your layers are ordered correctly too.
Double check that your text is not reverting to the default of Black, which would make it impossible to see the font on top of Dark Blue while typing.
Secondly I recommend blinding, hiding, making invisible the Dark Blue layer while you are typing.
Also have you created a text box, or are you just clicking and then starting to type? This will cause your type to go to the upper corner of the box on layer 2 which will insert it into that layer (this is me assuming that your dark color is a box and that that box is not locked. The Type cursor with have () around it and not the [] that indicates you need to click and drag to create a text box or the "I" which indicates you can begin typing.
I hope that this in some way helps if not can I get more information about what is going on? That way I can help you further.
HTH!
InDesign CS, Photoshop CS, Illustrator CS, Acrobat 7
Windows XP & MAC OS X (Yes I Use Both, Not at the Same Time)