Having a technical problem with the Customer Portal

[Stefani Kaimakliotou]

A customer created a request in the portal and then a Service Desk agent closed that issue. A few days later that issue was reopened automatically by another customer without actually doing anything. The second customer was trying to create his own request which was successfully created, but at the last screen instead of showing his own request, the reopened issue was shown. Since that day and every few days the particular issue is reopening with the same comment made by the second customer. 

I have no idea where to look and solve this problem and why is happening only to this customer. Any help?