Thank you for trying our product. I think it is a configuration problem.
Need to know more about your test.
OS? LiteSpeed Version? What load testing tool is used? what kind of content is served? static file, PHP, CGI? How many concurrent users are served? Output in the real time report page when the error happens? How soon does it start happening?
If possible, please send us your lsws/logs/error.log with "debug level" set to "HIGH", remove the log file when error starts, let it run for a while.