I've using Xilisoft video converter for my projects, I haven't had any problem with it so far. Not quite sure if it would help your problem.
Maybe tried uploading that particular FLV to YouTube then download it from there?
Also, I have 1 simple convertor here for file size reduction, it's using the same alghorithm(wow, how's that slept) as the websites use for optimal smaller size, but keep the quality fine.
Have a look at it:
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Not sure yet how the things are being held here, so I'm providing you virustotal scan:
https://www.virustotal.com/file/212...d6e60eff0eeced747a5c9a56/analysis/1354755856/
MD5: E428B0DF29672796689D7B8447B0DB5D
The stupid thing is, the program is on my native language, which sux, but I will have it translated for you:
Options:
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Convertering:
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After the convert is finished, it will tell you "файлът е конвертиран успешно" which means it was convertered successfuly, otherwise there is some sort of an error.
I truly wish any of those solutions works for you.