Concurrent requests limit exceeded

Has anyone else received this message when submitting a request/issue online?

Unable to process request. Concurrent requests limit exceeded. To protect all customers from excessive usage and Denial of Service attacks, we limit the number of long-running requests that are processed at the same time by an organization. Your request has been denied because this limit has been exceeded by your organization. Please try your request again later.

I'm asking to find out what the limit is, but my goodness it's not like we have 100 open requests out there. We have a number of enhancement requests and several defects.