I downloaded, extract and tried to upgrade to 6.4 but my tiki crash (error 500).
then looking in the log : error in files
Look in files and saw that in some files end of these files are corrupted.
Which package did you download? (zip, gz etc). And how are you uploading to your server - FTP?
We haven't had any reports so far about these being corrupted, are you sure it didn't happen on the way up to your server? Might just be worth sending them up again...
Will investigate if you let us know which file is the problem (the ones i tried were fine)