After this a new reboot seem to bypass the problem but the network don't work fine on the host system... analizing the crash dump i see a crash in NDIS.SYS where is involved the VB Network adapter driver, i've ignored this BUT this morning the network don't start at all (i see the driver in the system hardware panel BUT there are no network in the icon in the notify area).
The only solution i've found it's the SYSTEM RESTORE then i've restored the system BEFORE VB 4.1.20 and all work fine now.
My OS Windows 7 Professional 32-bit and my network adapter is Realtek PCIe GBE Family Controller with latest drivers available 7.3.522.2009 (and NDIS 6.20) (WiFi not used/disabled).
Bye.