The cooler answer can be found here
*www.thinkdigit.com/forum/cpu-motherboards/143907-cpu-best-e5800-c2d-7500-a.html
Hibernate mode saves everything from mem to disk and then shuts down the Pc - your comp can't come back from Hibernate mode to normal working state unless you start your comp by pressing the power switch
What you are seeing is your comp is coming back from Sleep Mode and There could be many reason behind it - most probably the sensor of the optical mouse can be the issue - I know it from personal exp
S3 is better Sleep mode than S1 an it saves more power and S4 means Hibernate mode - I think that clears out your confusion