Annotations not highlighted on pages on load

We experience an odd problem of inline annotations (text passages marked and annotated pressing Strg + m) not being properly highlighted after the page is reloaded. The annotations are shown in the comments tag and the annotation tab respectively, but on the page they only appear (together with their little note icon) when another annotation has been added. They disappear on the next reload.
The configuration in the admin section should be OK - we have a copy of the system running as a test version where everything works just fine. Any ideas?

I have to withdraw my complaint. Emptying the browser cache brought everything back to normal.