Get the message 'Invalid Design File' or 'Unable to Open File' error.
If it is a DGN file, the first thing to check is that you are not trying to open a V8 file in V7 or earlier MicroStation.If it is a DWG file, check the AutoCAD version the file is in. Then check if that version is compatible with the version of MicroStation you are using to open the file.If there are no version mismatches:1. Start MicroStation to the MicroStation Manager screen2. Left-click the File drop-down menu3. Select New4. Set the File Type to the type that the corrupt file is5. Give the file a name6. Make sure the seed file is the proper type7. Select OK8. Select OK again9. Reference in the corrupted fileIf the corrupted file doesn't show, go to step 2 for the corresponding file format.If the corrupted file does show:1. Detach all reference files from the corrupted file (they are now nested references)2. Left-click on the File drop-down menu3. Select Save As4. Append the file name with _015. Make sure the Select Format To Save drop-down matches the file format of the corrupt file6. In the lower right-hand corner left-click on Options7. Select the References tab8. Left-click on the External Attachments drop-down9. Select Merge10. Select OK twice.11. Reattach all reference filesIf the above doesn't work what you do next depends on the format of the file.For V7 format : run EDG on the file.