If you made changes to a document someone else has checked out, you will be prompted to save a copy of the document locally. The next time you open the document, Word will ask whether you want to merge your changes back to the source document. If you don't re-open the document after it has been checked back in, you won't be prompted to merge your changes. So if you have to save the document locally, be sure to check back later to see whether the document is available for editing. If it is, merge your changes back into the main document.
If the team site administrator has turned on versioning for your site, you can hover your mouse over the document name and click Version History. You can select an earlier version of the document to open or even replace the current version with the earlier version. Just be aware that if you replace the current version with an earlier one, you'll lose any changes made to the current version.
Occasionally, you might run into problems opening a document from a team site. The most common problem in opening a document from a team site is that the document simply hangs on opening. This can be caused by several problems. Examine the potential problems to determine which one is the cause of your issues. First, make sure that you have a good-quality connection to the SharePoint server. If you're on a dial-up line with significant static, you might have problems opening a document, especially if the document is large. The static can interrupt the loading of the document, and the Web site will appear to hang without actually opening the document.
The second possibility is that your document is corrupted. Check out a previous version of the document to determine whether other versions will open. If so, see whether another user can open the current document. If not, you might need to abandon the current version and revert to a saved version.
The third possibility is that you're trying to open a subdocument of a master document stored on a SharePoint team site. Currently this functionality is not supported. You should be able to open a standard document, but subdocuments will not display properly; instead, only a blank browser window will open.