Due to GDI+'s deferred image loading (especially of large files) the passed reference (e.g. an Image or MemoryStream) did not necessarily contain the physical file contents. When that reference is used to create thumbnails while the original Stream is not longer available you will receive a "General Exception in GDI+".

The workarounds are: 1. work directly with the file - would need some code refactoring, 2. flush the stream and write a temporary file.

h4. Steps to Reproduce
Use files with preferable large embedded cover images.
Example: "07 - Another Sunday.mp3" on TestFTP.