Graphics gone, mouse cannot move

[Elfenlyte]

I'm on an aluminum 20-inch screen iMac with 1 GB RAM and 128 megabytes of VRAM...

Now when I open PS, I cannot move the mouse. Well first of all the mouse does not show up in the first place... And there are no background graphics, etc...

Any ideas?

EDIT: Here are my stats for my Graphics Card:

ATI Radeon HD 2400 XT:

  Chipset Model:   ATI,RadeonHD2400
  Type:   Display
  Bus:   PCIe
  PCIe Lane Width:   x16
  VRAM (Total):   128 MB
  Vendor:   ATI (0x1002)
  Device ID:   0x94c8
  Revision ID:   0x0000
  ROM Revision:   113-B2250A-207
  EFI Driver Version:   01.00.207
  Displays:
iMac:
  Display Type:   LCD
  Resolution:   1680 x 1050
  Depth:   32-bit Color
  Built-In:   Yes
  Core Image:   Hardware Accelerated
  Main Display:   Yes
  Mirror:   Off
  Online:   Yes
  Quartz Extreme:   Supported
Display Connector:
  Status:   No display connected

[Merlin]

I have the same probleme somtimes. It's not special for mac. I
 have also my player who turn on himself . I resolve that problems as that  : I push on right and left rotation in the same time.
Thank you
Merlin