Here are some common situations:
1) The file begins to open, but stops and returns an error number -36 or -39.
This means that the file is actually physically damaged on the disk, or the operating system cannot handle the file. The first test is to see if you can make a copy of the file. Try dragging the file's icon to another disk or select it and choose Duplicate under the File menu from the Finder. If it won't copy, then the file is damaged and you can probably only get it to open using a utility that repairs damaged files, like Symantec Utilities or Norton Utilities. If the file does copy, read the following paragraphs and follow those suggestions.
2) The file begins to open but it stops and you get an out or memory error.
The file probably has a corrupt object, or it may have damaged resources. Try opening a new Claris CAD file and using the Place file... command to insert the file into the new file. If the original file has damaged resources, this may allow you to save the drawing. You can also use ResEdit to copy new resources to the file.
If the file will not place into a new file, then there is probably a corrupt object in the document. Try using a translation utility (like the Claris Graphics Translator) to see if translating the file to and from another format will filter out the corrupt object.
3) The file opens, but every time that you click on the drawing or try to move something you get the "sorry, objects must remain within document boundaries" error message.
This is caused by having an object that has a coordinate off the drawing boundary. The program will give you this message every time that it thinks that it has to redraw or move the suspect object. There are several strategies for finding and removing the object:
1) Go under the Layout menu to Fit to Window. You will probably see several seemingly blank pages or handles (the little rectangles that surround an object) that don't seem to be attached to an object. See if clicking on one of the blank pages will show you some handles. If so, hit the delete (or backspace) key on your keyboard. If you don't see any handles, try to click-drag the arrow cursor around your drawing to select everything on it. Don't surround the blank pages. See if you can copy the items to a new file.
2) See if you can go to another layer and copy and paste that layer to a new document. Sometimes hiding the layer with the corrupt document will allow you to copy and paste the other layers to a new document.
3) Try using a translating utility like the Claris Graphics Translator to translate the file to and from another format.