The Unexpected End of File error indicates that the End of File marker located in the header information of the project is either missing or, if present, indicates an end of file location where no data for the file can be found. File damage of this type can sometimes be recovered if the project still has data in it, and only the header information of the file is damaged.
Any number of variables can cause file damage. Most damaged files are the result of an incomplete save. An incomplete save may occur if the application unexpectedly quits, the system fails while saving a project, or if the network goes down while saving a project to a network drive. Files can become damaged if you save a a project to damaged media, or if the media becomes corrupted at a later point in time. Depending on the degree of damage, you may or may not be able to recover the project.
On Mac OS, click on the project file to select it in the Finder. Then go to File > Get Info (or press Command )to get information about the project, and look at the General Information in Get Info window on the Finder level. If the file size is either zero or much smaller in size than the original file size, the project is probably not retrievable. But if the project appears to be the correct size, copy the project to a new folder on the hard drive and rename it test.qxp.
If you do not have a backup file, try copying the file between drives or from a Mac to a Window machine. By dragging the project to a different disk or drive, it is rewritten and it may then be possible to open the project. Since QuarkXPress for Mac OS and QuarkXPress for Windows access the file header differently, you may be able to open the project on one platform and not the other. Then it could be resaved and brought back to the original platform and used normally.