Does it still have the right click options that you would expect from an excel embedded object?
Or has it completely been replaced with a normal shape?
A few things I could think of which might be worth of checking:
- 1) Check if the file still exists ( at the location Visio is looking for it )
- 2) Open en save the excel file again (2003 format again)
- 3) Do the same with Visio (As long as its still an embedded item and not a simple shape)
- 4) Check the shapesheet of the embedded object, see if you find anything odd (Probable not gone find anything)
- 5) Try some of the object options, converting, opening etc.
As for the reason why it happened... Could just be that a crash, or wrong save corrupted the file. Re-embed the excel data and hope it doesn't happen again? Had some problems caused by this, but of its not, no clue what could be the reason.