OS 10.6.8 losts connection with Windows. What do I do?

Hi!

I work with graphic design and here, there is a network with 3 pcs (running windows 7 64 bits) and a Mac OS 10.6.8. I'm not an expert in macs and I'm having a problem. All the files, like psd and vector files, are stored in an external HD in an windows computer and the Mac access those files by network using smb protocol (e.g. smb://192.168.1.12).

The problem is: sometimes, with no clear reason, the connection is lost and the mac can't reconnect.

Restarting the computer with the hd solves the issue, and sometimes the connection returns withou doing anything.

I can notice that sometimes the the problem appears when other computers on the network saves big data or transfer big amount of data.

I looked across the internet and found some similar problems:

https://discussions.apple.com/thread/2443735?start=0&tstart=0

https://discussions.apple.com/thread/2546874?answerId=12112679022#12112679022

But both discussions didn't help me. Anyone can try?

(Sorry for my english!)