I am also having the same error - I have a:
Mac Pro (Mid 2010)
2.8 Ghz Quad-core Intel Xeon
7gb memory
machdep.cpu.max_basic: 11
machdep.cpu.max_ext: 2147483656
machdep.cpu.vendor: GenuineIntel
machdep.cpu.brand_string: Intel® Xeon® CPU W3530 @ 2.80GHz
machdep.cpu.family: 6
machdep.cpu.model: 26
machdep.cpu.extmodel: 1
machdep.cpu.extfamily: 0
machdep.cpu.stepping: 5
machdep.cpu.feature_bits: 44160500475100159
machdep.cpu.extfeature_bits: 4967106816
machdep.cpu.signature: 67237
machdep.cpu.brand: 0
machdep.cpu.features: FPU VME DE PSE TSC MSR PAE MCE CX8 APIC SEP MTRR PGE MCA CMOV PAT PSE36 CLFSH DS ACPI MMX FXSR SSE SSE2 SS HTT TM PBE SSE3 DTES64 MON DSCPL VMX EST TM2 SSSE3 CX16 TPR PDCM SSE4.1 SSE4.2 POPCNT
machdep.cpu.extfeatures: SYSCALL XD EM64T LAHF RDTSCP TSCI
It has “VMX” listed in the features and my firmware is up to date. so it should work?