1. Exit LW from tray. Run scandisk

2. If your antivirus has detected supect files in your downloads than it stops the acces to them... so if LW is unable to acces them than it says disk problem

3. If the files with the error are some of the old downloads (from the old LW) than you shoul cancel them and restart all from searching.

4. You can try to acces your files: goto Library->Incomplete Files. Here hit Explore. A folder with your files will open. After an antivirus scan you can try to acces them to see in what condition they are.