Timesheet filter displayed in one column only

[peegee]

I am using the time-sheet extensions in two installations of redmine 1.0.5.
While the one installation displays the timesheet filter dialog as in your screenshot (and as expected) in multiple columns, using the width of the screen, my other installation only seems to use one column.
If I click on "Timesheet", I can see under each other (instead of beside each other)
Period
From
Sort by

Technically the filter works, but it makes it difficult to select the wanted filter criteria, as a lot of scrolling is needed. Any idea of how to fix this?