If I press control+H or click on the Replace button on the toolbar, nothing happens. The Replace tool doesn't appear. This happened suddenly. I rebooted but the problem persists. Any idea what could have gone wrong?

There could be a fault in Office installation. Have you tried repairing it (via Start > Windows Control Panel > Programs > Programs & Features > Microsoft Office (version) > Change)?

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]

Thanks, Paul, but it's a company computer and I have no control of the installation. I can call the help desk when I need to (they're in shouting distance).

It happened only with one document. I noticed that when control+H did nothing, if I pressed control+F, the Find menu would come up, and sometimes then I could get the Replace menu with control+H.

I can't post the document because it's proprietary, but I'm suspecting that there was something corrupt in it.

Corruption may well be the issue, as I know of know document-specific feature that would allow Find but not Replace for an individual document.

Corrupt documents can often be 'repaired' by inserting a new, empty, paragraph at the very end, copying everything except that new paragraph to a new document based on the same template (headers & footers may need to be copied separately), closing the old document and saving the new one over it.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]