When I'm facing enemies, the fire button sometimes doesn't respond when firing non-automatic weapons (e.g., 10mm pistol, laser pistol) rapidly outside of VATS. This isn't a mouse issue, as it also occurs when I set attack to the the keyboard. I'm pretty sure it isn't a general issue with inputs; I've tried hitting movement keys rapidly while facing enemies and had no cases of unresponsiveness. This doesn't appear to be a performance-related issue either, since my framerate is quite good when this occurs. I also know that I'm not firing the guns too quickly, as this occurs even which I press attack at a rate well below the weapons' rate of fire. Any help that could be provided would be very much appreciated. I've included some information about my computer below.

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System Information
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Time of this report: 1/28/2011, 18:49:09
Operating System: Windows XP Professional (5.1, Build 2600) Service Pack 3 (2600.xpsp_sp3_gdr.100427-1636)
Language: English (Regional Setting: English)
System Manufacturer: Gigabyte Technology Co., Ltd.
System Model: EP35-DS3L
BIOS: Award Modular BIOS v6.00PG
Processor: Intel® Core™2 Quad CPU Q6600 @ 2.40GHz (4 CPUs)
Memory: 3582MB RAM
Page File: 3643MB used, 1821MB available
Windows Dir: C:\WINDOWS
DirectX Version: DirectX 9.0c (4.09.0000.0904)
DX Setup Parameters: Not found
DxDiag Version: 5.03.2600.5512 32bit Unicode

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Display Devices
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Card name: ATI Radeon HD 4800 Series
Manufacturer: ATI Technologies Inc.
Chip type: ATI Radeon Graphics Processor (0x9442)
DAC type: Internal DAC(400MHz)
Device Key: Enum\PCI\VEN_1002&DEV_9442&SUBSYS_E104174B&REV_00
Display Memory: 1024.0 MB
Current Mode: 1920 x 1200 (32 bit) (60Hz)
Monitor: Plug and Play Monitor
Monitor Max Res: 1600,1200
Driver Name: ati2dvag.dll
Driver Version: 6.14.0010.7111 (English)
DDI Version: 9 (or higher)
Driver Attributes: Final Retail
Driver Date/Size: 8/3/2010 20:46:04, 300544 bytes

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Sound Devices
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Description: Realtek HD Audio output
Default Sound Playback: Yes
Default Voice Playback: Yes
Hardware ID: HDAUDIO\FUNC_01&VEN_10EC&DEV_0888&SUBSYS_1458A002&REV_1000
Manufacturer ID: 1
Product ID: 100
Type: WDM
Driver Name: RtkHDAud.sys
Driver Version: 5.10.0000.5567 (English)
Driver Attributes: Final Retail
WHQL Logo'd: Yes
Date and Size: 2/14/2008 04:04:06, 4676096 bytes
Other Files:
Driver Provider: Realtek Semiconductor Corp.
HW Accel Level: Standard
Cap Flags: 0xF5F
Min/Max Sample Rate: 8000, 192000
Static/Strm HW Mix Bufs: 33, 8
Static/Strm HW 3D Bufs: 33, 8