You can NOT mix 32 and 64-bit code in the same process. When you installed the 32-bit OWC11 components, that's exactly what you tried to do.
You really have no choice but to abandon OWC. There is no 64-bit version and there are no plans to develop the library any further. This was back in 2007(?)...
The only replacement for what you're doing, from MS, that I know of would be Excel Services.
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