virtio driver with WinXP breaks connection to FileMaker Server since upgrade to 4.1.4

[virtwolf]

The setup: A LAN with three virtual Windows XP machines on one and a Windows Server 2003 installation running on another Linux (Debian Squeeze) host, both with latest VirtualBox 4.1.4 installations and Extensions. All virtual machines have their designated bridged tap interfaces on the respective Linux hosts.

The XP machines have FileMaker Pro 11 clients installed, the server has FileMaker Server 11. Two FM clients can log into the FM database, the third one does not get through. I can ping from the underlying XP to the W2K3 server but that is all. The error from FileMaker server is

Warning 200 SERVERNAME Client "(hostname) [192.168.1.99]" denied access because the license key is already in use by client "myusername (hostname) [192.168.1.99]"

The problem was the broken XP client system's network configuration: It was connected to the LAN through a RedHat VirtIO network driver (Adapter 2) with which I had been experimenting a while ago. Simple switching back in VirtualBox to the previously installed Intel (R) PRO/1000 MT driver (Adapter 1) restored full FileMaker network functionality. The other clients also use the Intel drivers.

I am not sure whether the problem is the use of the virtio interface per se or the fact that both virtual adapters, virtio and Intel, were configured with the same IP address (had to click away a Windows alert to confirm this setting) and therefore perhaps the request from FMPro that went to FMServer may have been passed through both Windows guest interfaces simultaneously although the device manager only shows one interface. However, logging into Windows via a remote rdp connection while using the virtio interface triggered the Windows jingle and shortly afterwards I could hear a second jingle, like an echo. This does not happen when the Intel driver is being used.

It is also not clear how exactly the upgrade from 4.1.2 to 4.1.4 could have caused the problem. It appeared after the upgrade but I do not know whether it may have swapped the activated Adapter from Intel to virtio (both were previously installed but only one was activated), or has something in the previously functional virtio driver been changed for worse?

[aeichner]

Please reopen if still relevant with a recent VirtualBox release.