Problem solved. I updated the driver for my video adapter. Its OpenGL , intergrated on my intel board. Older versions of Maya seemed to work fine on this machine so it took me awhile to suspect...

But I have a registered educational version of Maya 7 unlimited.
I reported this to Alias's support center but as a 'bronze' patron I am not sure what to expect in the way of replies. I did try...

Hi.
I have an educ. version of maya 7. For some reason my cameras disappear from the all viewports when I select nurb objects. (with only polygons in the scene everything is fine). The cameras will...