I am trying to take screen snap-shots with the shortcut keys of
- cmd + Shft + 4 and
- cmd + Shft + 3.
I am not getting the proper screen-shots. This is one of the examples:

What would be the reason behind these blurry screen-shots?
MacMini: Intel Core 2 Duo, 1 GB RAM, Older model
Monitor: Dell Monitor - 15"
NVIDIA GeForce 9400:
Chipset Model: NVIDIA GeForce 9400
Type: Display
Bus: PCI
VRAM (Total): 128 MB
Vendor: NVIDIA (0x10de)
Device ID: 0x0861
Revision ID: 0x00b1
ROM Revision: 3362
Displays:
DELL E773c:
Resolution: 1280 x 1024 @ 60 Hz
Depth: 32-Bit Color
Core Image: Hardware Accelerated
Main Display: Yes
Mirror: Off
Online: Yes
Quartz Extreme: Supported
Rotation: Supported
Display Connector:
Status: No Display Connected