Do you know if your Work partition crosses a 4GB boundary (e.g. starts 3.8GB in to the disk and ends 4.3GB in to the disk)? If so then this is your problem (3.0 and 3.1 using the default filesystem cannot see more than 4GB. If you go above 4GB then it causes corruption).
If you switch off or reboot when data is being written then corruption can occur. You could download DiskSalv from Aminet and try to repair the partition, or you could copy the data to another partition, then format the Work partition, then copy the data back.
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moto