It's been a fair old while since I've looked at the nicesplice code, but I'll try and find some time soon to see if I can recreate this problem. It certainly looks like it's down to the size of the recording - it was quite tricky getting support for files of > 4 gigs in, and there may be some problems in there. There are a couple of buffers that assume the recording will be less than 8 hours, but I see this was 6 so should be ok with that. Can't promise anything within the next week, but hang on to that recording for now...