Possible but not probable. Overclocking ability has many factors, but to my knowledge the VIA drivers (or lack of) have nothing to do with it. Overclocking is related to how high a multiplier your CPU can handle, how high (FSB) your memory can go and the rest of your systems' ability to handle the increased PCI/AGP bus speeds.
The reason your system hasn't crashed and burned is probably b/c you're not using an AGP card. I've seen Socket A mobos that will hang in Windows within a few seconds w/o the VIA AGP busmastering driver installed.
BTW, your OC is pretty decent. I have a 1GHz TBird (B) that can only handle a 10.5 multiplier, else Windows locks at the desktop. Be happy.