Do you get an error?

Did you check the error log?

No error page is displayed and there are no errors in the system log

Just tested this on here and all is working as expected.

What happens when you click update?

I click a version from the project overview page.
Then click batch update at the bottom of the list of issues.
On the batch update screen I deselected all and then select a couple of issues from the middle of the list.
I leave all the settings on the right as default and only change the fixed for version number and click update.
The page reloads and I am returned to the list of issues for that version, but the issues I selected to move are still there.

We updated to V3.5.1 from V3.1.1 yesterday and since then we have been unable to do batch update.

DaveMac,

Send your contact details over to our support email address and one of the team will be in touch to help you resolve this issue.