But my Macbook Pro works fine with Mac/OS, if there is a disk problem, shouldn't I also have a problem then?
You would notice the problem in the way of sluggishness, freezing, beachballing, possibly crashing, however it's not always the case.
Basically, the I/O error is put up when we ask for some data on the disk, but OS X replies with 'I tried to get it, but couldn't for an unknown reason'.
It's entirely out of Fusion's control.
Now HFS, the Mac's file system, is smart and will dynamically shuffle around data from a bad sector if possible.
Sometimes the data in the bad sector is recoverable, sometimes it isn't.
The sector happens to be where your Virtual Disk 'lives' on the hard drive, which is why other apps and OS X haven't had noticeable symptoms yet.
Indeed, it's probably a matter of time before things get worse, so I'd take the time to backup what you can now.
Have AppleCare review the I/O errors in the logs and give you an explanation as to why they're there. (You might need to talk to a 'Tier 2' agent who will actually know what they mean)