ports problem in cubase 5 LE?

hello
I have installed LEXICON Alpha device with Cubase 5 LE software on my computer.
every thing worked fine up to this point.
then , I have installed and added as VST PLUGINS the following software’s:

  1. AmpliTube 3 - guitar effects.
  2. ezdrummer – drum machine.

and from that point , I have the following problems:

  1. when i open the software i get a “missing ports” alert.
  2. I cannot record through the Cubase software. When I plug in a microphone, I hear it in my headphones, but the software does not “hear” and record it.
  3. When I open the Drums software via Cubase, there is no sound at all (or record).
    4 .I do not hear any sound notification such as the metronome or the beginning of recording beeps.
  4. i hear windows sound via the device headphones and cannot hear the device and regular voices (youtube at the same time for exsample) at the same time.

I’m pretty sure that an audio ports problem.
but I do not know how to fix it.
Please help me.

thank you, omer.