BSOD with Acer Veriton M275 after adding Asus EAH4350 Silent

I've recently added the EAH4350 to be able to attach a second monitor.
The video card always worked regularly in a previous PC (not with windows though).
Now from time to time and in a apparently random fashion the system hangs with a BSOD. The system is always used for very lightweight office work (Excel, browsing, ...).

I've followed the instructions for BSOD posting, attaching the output from SF_Diagnostic_Tool collected just after the last freeze. Before I've enabled minidumps.
Is there anything I can try?

Thanks in advance for any help.
Cheers,
Marco

Update your ATI Radeon HD 4350 driver: AMD Catalyst