Suspicious network activity advice

Could anyone offer me some advice or guidance with this please. 

I am developer and have been suspend from work because of suspicious network 
activity. Its a corporate network (local government) predominantly running a 
combination Microsoft OSs across many sites. 

It seems that many computers on the corporate network have entries in their 
event logs to say that my system logged onto these machines for any instant. 
This happens three times of the course of a single day and but second time my 
computers events log shows that each of these computers have logged back into 
my system. 
The IT audit section sent the computer away and it came back clean e.g. no 
viruses and their stance seems to be that they dont know what has happened but 
they believe that I have used some kind of scanning software. 

Im trying desperately to find another explanation for this, can anyone suggest 
what might have happened. Could using something like visio or a simple file 
search across the network produce similar activity? 

They did seems to think that it was relevant that each computer was contact in 
alphabetical order not IP order. 
Any help would be greatly appreciated.