The information you offered is not suitable to even make an educated guess.
Could be a temporary problem with your server. Could be a database problem.
Did you check the problem with different surveys. Create a copy of the survey and create a new survey. Same issue?
You could update LS, but I would encourage you to stay on 2.05 (even though security update weren't fixed there).
Jelo is right, there is very little information we can work with.
For us to be able to help we would need sem information about your survey, the type of conditions, how many conditions, how big is the survey, do other surveys run fine, is it with a very specific condition or with all conditions, etc.
Help us to help you!
Provide your LS version and where it is installed (own server, uni/employer, SaaS hosting, etc.).
Always provide a LSS file (not LSQ or LSG).
Note: I answer at this forum in my spare time, I'm not a LimeSurvey GmbH employee.
The survey is small.
I just have 2 questions. Just set the 2nd question with the condition with 1st one.
It is very slow response once I click "Add condition".
even though I cannot access survey again. I need to close the browser.