I don't know if this issue is caused by the portable version but it's been twice that happens to me. I am using version V3.2.0, windows XP SP3.
I downloaded two large files from different sites. One is near 293 Mb and the other 1.5 Gb. In both cases, filezilla didn't stop downloading the files, it simple kept downloading the files so I had to cancel the process as they were becoming too large, almost as twice as their original size, the advance percentage was greater than 100%.
Fortunately, one file was a zip file and although winrar reported as corrupted it was able to extract the content. The other was an exe autoextractable file, this time, winrar wasn't able to extract it but the autoextract feature did the job -running the file-. It seems like once the file was about to be finished it started all over again appending all together.
What happened? I've just used Filezilla few times and there is not such a good taste in this.
This is one link if somebody wants to try it:
ftp://betaftp3.mapinfo.com/products/mapinfo/MI95/MiPro951_b62.exe (293 Mb)