VirtualBox4.3.16 custom device error:Bad printable string

[zhao]

environment: VirtualBox4.3.16, win7 x64
when i add custom device EventDevice.dll to VirtualBox, then start vm, get the error as follow:
VMSetError: Unable to load R3 module C:\Program Files (x86)\Windroye\EventDevice.dll EventDevice): RTCRX509ATTRIBUTETYPEANDVALUE::Value: Bad printable string: ch=0x40: \Device\HarddiskVolume1\Program Files (x86)\Windroye\EventDevice.dll
00:00:01.292165 ERROR [COM]: aRC=E_FAIL (0x80004005) aIID={8ab7c520-2442-4b66-8d74-4ff1e195d2b6} aComponent={Console} aText={Unable to load R3 module C:\Program Files (x86)\Windroye\EventDevice.dll (EventDevice): RTCRX509ATTRIBUTETYPEANDVALUE::Value: Bad printable string: ch=0x40: \Device\HarddiskVolume1\Program Files (x86)\Windroye\EventDevice.dll (VERR_ASN1_INVALID_PRINTABLE_STRING_ENCODING)}, preserve=false
00:00:01.347716 Power up failed (vrc=VERR_ASN1_INVALID_PRINTABLE_STRING_ENCODING, rc=E_FAIL (0X80004005))

Can somebody tell me why?

[zhao]

Is it that Digital signature caused the above problems ? If it do, what are the Digital signature requirements in new version VirtualBox4.3.16 ? In VirtualBox4.3.12, the EventDevice.dll run well without Digital signature.