Vista - Final Fantasy XI - Pausing - Hesitating

This seems to only affect the game Final Fantasy XI on my computer. Games
like Command and Conquer 3 work fine.
I can install FFXI no problem it updates Play Online Viewer and the game
with no problems at all. Its when i come to run the game it works for a few
seconds then pauses, then runs for a few seconds then pauses etc. its not lag
from within the game as it does this jumpy problem on the character login and
a little on the Play Online Viewer (only scrolling text). This is really
bugging me now and i want to keep using Vista but it looks like i might go
back to XP.

Im running a good spec machine from dell. All drivers are upto date as far
as i can tell. Anyone with a suggestion or solution is most welcome. Thank
you.

------------------
System Information
------------------
Operating System: Windows Vistaâ„¢ Home Premium (6.0, Build 6000)
(6000.vista_rtm.061101-2205)
Language: English (Regional Setting: English)
System Manufacturer: Dell Inc.
System Model: Dell DM061
BIOS: Phoenix ROM BIOS PLUS Version 1.10 2.3.2
Processor: Intel(R) Core(TM)2 CPU 4300 @ 1.80GHz (2 CPUs), ~1.8GHz
Memory: 2046MB RAM
DirectX Version: DirectX 10
DxDiag Version: 6.00.6000.16386 32bit Unicode
---------------
Display Devices
---------------
Card name: Radeon X1950 Pro
Manufacturer: ATI Technologies Inc.
Chip type: ATI Radeon Graphics Processor (0x7280)
DAC type: Internal DAC(400MHz)
Display Memory: 1278 MB
Dedicated Memory: 511 MB
Shared Memory: 766 MB
Current Mode: 1280 x 1024 (32 bit) (75Hz)
Monitor: Dell SE197FP
Driver Version: 7.14.0010.0503 (English)