this board should support 2nd and 3rd generatie i5 processors.
support both 2nd and 3rd gen i5 processors with the proper BIOS version. However, you have to remember that the 6-series chipset (H61 for example) was released with Sandy Bridge, one year before Ivy Bridge came out. While I have seen motherboard manufacturers update the "shipping BIOS version" over time, it's not something you can just take for granted. That really depends on the company and/or how long the board has sat on the shelf. For your motherboard, the 3605 BIOS revision that supports the i5-3450 was released in March 2012, so if the mobo was built before then, chances are good that it didn't ship with that version. The only guarantee when you buy a mobo is that you'll get the lowest BIOS version number, or in this case, the one labeled "release BIOS."
Now, I don't know if you got another of the exact same motherboard or not, sounds like you'll never know if it was the BIOS version on the original mobo or not, but I've learned this lesson the hard way. BTW, I believe this issue makes up a large portion of DOA mobo reviews on newegg.
Main: i5-3570K, ASRock Z77 Pro4-M, MSI RX480 8G, 500GB Crucial BX100, 2 TB Samsung EcoGreen F4, 16GB 1600MHz G.Skill @1.25V, EVGA 550-G2, Silverstone PS07B
HTPC: A8-5600K, MSI FM2-A75IA-E53, 4TB Seagate SSHD, 8GB 1866MHz G.Skill, Crosley D-25 Case Mod