Sounds like the .twk file is corrupt. Does this happen with just one file or all? There may also be a problem with your decimal seperator, try changing this from a comma (,) to a period (.). You can find the option in Windows under Regional & Language Options in Control Panel.
Would you mind dropping me a PM from your licensed account to back up that statement?
No, it`s does not work with the latest released versions of LFS
So the only way for you to use Tweak is to install LFS version V, and then install tweak.