Problems with nikon D90 camera pop up flash?

I have a Nikon D90 that is a little over a year old. Lately it has been giving me issues. I will go to take pictures mostly in Manual, but I get F- - in the top screen. When this happens I can't take any photos and I just have to wait a few hours for it to return to normal. Now a new problems has occurred that the flash will not work. The screen turns blank and nothing happens but it will take the photo just fine with out the flash, though I need the flash to take the majority of my photos as many places have poor lighting.

See page 255 in your manual for error codes. The F-- means the camera doesn't see your lens. This is a common problem with Nikon kit lenses (18-55 and 18-105) and is probably due to dirty electrical contacts on the lens. The solution is to gently rotate the base of the lens back and forth like you are trying to remove the lens, but without depressing the lens release button. For bad cases, you can try removing the lens and attaching again. If this doesn't fix the problem, you need to send the camera in for repair.

The flash is another problem. You will need to get this serviced. Call Nikon. On some Nikon models, a contact slips off on the flash mechanism. There are videos showing how to fix the D40 flash, but you need to know what you're doing or you will get electrocuted or damage the flash/camera. If the flash repair is too costly, you can buy a SB400 flash, which is better than your built in flash, for around $120.