I have upgraded from Access 2000 to Access 2010 64bit and I've noticed very serious performance problem. For example a simple query is 10x slower.

This is a known issue of Windows 7 and Jet 4.

I've found some solutions. The best one is to modify a key registry for Jet engine, the MaxBufferSize from 0 (auto-calculated) to 20000, to 100000 and to 300000. Link

I've also tried Access 2010 32 bit, with no luck.

This solution improve performance and everything is very fast, but after some query

Have you got any suggestion?

Thank you!