Glitch?

I know this is a very small problem and usually will be fix after restart

http://i44.tinypic.com/1z17bk0.jpg
http://i41.tinypic.com/15rb5on.jpg


whenever i right click any icon on my tray it is black and will only show the option after i hover it. this happens when im using my pc for long hours base on my observation.

Anyone have idea whats causing this.? i think its not a virus. coz i regularly maintain my pc


Additional info

OS Name Microsoft Windows XP Professional
Version 5.1.2600 Service Pack 2, v.2082 Build 2600
OS Manufacturer Microsoft Corporation
System Name
System Manufacturer To Be Filled By O.E.M.
System Model To Be Filled By O.E.M.
System Type X86-based PC
Processor x86 Family 15 Model 4 Stepping 7 GenuineIntel ~2678 Mhz
Processor x86 Family 15 Model 4 Stepping 7 GenuineIntel ~2678 Mhz
BIOS Version/Date American Megatrends Inc. P1.40, 1/12/2011
SMBIOS Version 2.5
Windows Directory C:\WINDOWS
System Directory C:\WINDOWS\system32
Boot Device \Device\HarddiskVolume1
Locale
Hardware Abstraction Layer Version = "5.1.2600.2082 (xpsp.040216-1810)"
User Name
Time Zone
Total Physical Memory 2,048.00 MB
Available Physical Memory 1.05 GB
Total Virtual Memory 5.35 GB
Available Virtual Memory 4.07 GB
Page File Space 3.60 GB
Page File C:\pagefile.sys


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