schoent:
1016 Can't open file: 'whos_online.MYI' (errno: 145)
These errors indicate a problem at the database level.
It is not a bug in Zen Cart.
Kelvyn's suggestion above may help. If not, talk to your hosting company. You may have run out of disk space, or the server-file containing that database table may be corrupt in some other way. To fix the file, your server host needs to get involved.
Moving this post to "General" forum, since it's not a code-level bug.
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