Suspicious activities

Hi everyone,
in last 4 days Norton Tamper Protection show me 4 log entries in NIS Event History:

c:\windows\system32\svchost.exe
c:\windows\system32\spoolsv.exe
c:\windows\system32\services.exe
c:\program files\winzip\winzip32.exe

try to “create a file” in 

C:\ProgramData\Norton{0C55C096-0F1D-4F28-AAA2-85EF591126E7}\Norton\Definitions\VirusDefs\Cat.DB

the action was blocked.

NIS doesn’t detect any of suspicious. 

Is it possible that a virus is in the PC?

My system: Vista Premium 32 bit Italian with NIS 16.5.0.134 + AOP 3.7

Thanks in advance for replies.