Generally, when a file can not be opened it is an unsupported file type. You can check to make sure that the file you are trying to open is supported by Docs to Go going to our supported files page here. If the file is stuck in view only mode it might be because your excel document has an unsupported formula. You can click here for our list of supported formulas in Docs to Go.
If your file gives an error or crashes the program when you try to open it, it is likely due to a file being corrupted. This can be resolved by opening the file where it was originally created and open the file and do a save as to make a new copy of the file. After you have your new copy of the file send it back to Docs to Go the same way that you transferred it originally.