Noone reported such a behaviour yet....and the rebuilder is the most used part of ClrMame ;)

Could be different stuff:

- interfearing program like virusscanners
- via chipset
- bad RAM timing, bad HD, bad HD drivers, bad IDE cable

Try it with a different partition, different files, fiddle with the zipsettings, like enabling/disabling zipcache, enabling/disabling additional zipflush, try with or withour recompress. And be sure that ClrMamePro's temp folder got enough free diskspace.

Roman Scherzer
ClrMamePro