I am not able to reproduce your problem. Can you please provide additional information regarding the steps you follow to reproduce the problem, use of custom fields, plugins, etc...

Steps :

• Click on bug report
• Set fields
• Click on the button to add the bug
• The error appears now
  This error is very aleatory and appears when the network or the server is slow.

I'm using one custom field (combobox) and plugins Mantis Core Formatting and Mantis Graph (by the way : my graphs doesn't works)

Thanks

MantisBT Version 1.2.2
Schema Version 183

I ran across this same problem for the first time today. I had never previously gotten the error message, have no plugins or custom fields installed. I was able to repeat the process at least six times and was not resolved with logging out and then back in or closing my browser. I was then able to submit a bug report a few minutes later without problem.

I agree that it might have something to do with decreased responsiveness on the hosts' side.

HTH

Since both of you report taht the error seems to appear when the network or the server is slow, I'm not sure this is in fact a Mantis issue.

Problem most likely caused by php session settings.