cubase crashing!!

I currently use cubase ai8. It keeps crashing now!!
My set up is as follows…
Cubase ai8, with a samson graphite 25 midi controller and a Yamaha dtx multi 12 percussion pad.
For my Audio Interface, i use a Roland BR800 Digital Recorder.
These are all connected to my HP Laptop using widows 8 (4GB RAM)

Things were running ok at first, although i was having Clipping issues but this has been sorted.
I am NOT SURE if this is related but i recently purchased GARRITAN INSTANT ORCHESTRA, following research on availability and compatibility. All seemed well so made the puchase. It was after installation of this product that all the CRASHING seemed to start. Not only was cubase crashing but my audio input and output settings of my AI had lost all connection. Now, my AI is not being recognised by my computer, keeps telling me audio device not connected to computer. I have checked ALL cable/USB connections and they are fine but something is wrong somewhere.
I UNINSTALLED the Garritan IO product, thinking that its installation was the cause of the problems, but following this, when i start cubase, it tells me to choose audio device setting(BR800 or LOW LATENCY ASIO) and when i choose the BR800, IT IT USUALLY WHEN CUBASE CRASHES!!
I cannot make any headway and get going with the project i want to work on, this is very frustrating!!!
I have spent time (and a lot of money!!) on this and not managed to record a single instrument track to keep yet!
I have been trying to figure this out now for best part 4-6 weeks!!
Is there anybody out there who has had same or simillar problems, if so, could you please help if you can.
Any assistance would be very much appreciated!!!
If more info is needed then please let me know!!!
Many thanks to all who reply…