I've been trying to search the forums for this error, but couldn't find anything, so sorry if this is mentioned earlier.
I'm using Romcenter 3.57, but had this error with 3.56 too. When I rename roms (doesn't matter how: fix roms/advanced->rename roms/...) it starts, but after ~50 (or so) roms I get this error:

This is on the Amiga-dats (TOSEC), but also on the MSX-dats I've encountered it. (I only used those system-dats only)
I'm running Win7 64-bit.
Thanks in advance!