Unstable File Sharing on OS X 10.9.2 (successive errors with shared folders from pc's)

I'm new in mac world and my problem is this:

In my home, I have a domestic network with some shared folders between pc's (1 windows vista; 1 windows 8.1 pro; modem-router Technicolor TG784n v3).

With the new Macbook pro (OS X 10.9.2), I'm trying to use the same resources and communications between computers.

After some basics configurations, my mac recognizes the other two computers. However, when I try to access them sometimes that works, sometimes not. When it works, the process is very slow and, after some solicitations, the connection crash.

On Console, I identify some erros like this:

- kernel: smb2_rq_credit_decrement: Timed out waiting for credits 35

- kernel: smb2_smb_parse_change_notify: smb_rq_reply failed 60

- kernel: smb_iod_reconnect: Reconnected share XXXXX with server PC-W81

- kernel: smb_fid_get_kernel_fid: No smb2 fid found for fid 57550ef47cc64007

etc.

All this occurs when i try access a shared folders on windows pc's (not the reverse).

Any suggestion to resolve this?

Thanks