Horizontal scrolling does not work when viewing, creating or editing issues in IE7

When working with issues with long lines in IE7, the horizontal scrolling does not work. When creating or editing an issue, this leaves the user stuck in preview mode, unable to switch back to wiki markup mode or save the issue. When viewing an issue, this prevents the user from seeing any content to the right of the first screenful.

Creating an issue:
1) If Wiki rendering is not enabled, enable it by selecting Administration->Field Configurations->Default Field Configuration->Description->Renderers->Wiki Style Renderer.
2) Create a new issue and set the summary.
3) In the issue description, add a "noformat" block with a single long line of text.
4) Click the preview button to the right of the description field.

At this point, the page expands horizontally to show the content on one line. However, in IE7, a horizontal scroll bar is not created. This causes a few problems:

• The user can't see the content of the description field.
• The user can't see the preview button to return to wiki markup mode to edit the description further.
• If the line is long enough, the user can't see the Create button to create the issue.

There is a workaround - to tab through the fields - but it is non-obvious.
5) Press <tab> until the "Create" button is selected, and click it to go to the issue's view page.

At this point, the page has been horizontally expanded to fit the whole content, and a horizontal scrollbar is present. However, on IE7, if you scroll horizontally, there is only whitespace to the right of the first screenful.

Does not reproduce in IE6, IE8 or FireFox.