There are at least 5 hardware revisions of the 2008 Tomtom XL (which includes all flavors of the 325 and 330), each has similar features but runs slightly different software revisions. Depending on the model, they run 8.010, 8.080, 8.081, 8.082, or 8.083
I doubt the software is fully cross compatible with different hardware editions, since Tomtom has never offered a software update from one version to another. So I think the rep that offered 8.083 was incorrect, and the right version is 8.082.
It's sounding from these posts that there's a flash memory I/O issue, my guess is it's bad USB controller firmware rather than bad flash memory. USB controller firmware is controlled by the 5.5128 bootloader which was known to be flaky on the XL340 series.
With the XL 340 series, the problem was fixed by running application 9.x, which has the same booloader as 8.083. So maybe the app update will be a reasonable fix.