What Fireworks version and what operating system are you using?
Hello, I'm using Fireworks CS5 with Windows 7 64 bit.
Has this happened before—with other pictures? I'm wondering if there might be any issue with the location of these particular files that you're attempting to process.
Unfortunately, I don't have any great ideas on this. There's a folder called "Batch Code" within the application Configuration folder; I assume this contains the scripts used for the Batch Process feature. You might give this a quick look. Also, within your user Configuration folder (in the Adobe/Fireworks CS5 folder within your user-specific Application Data folder), there's a text file called "FireworksBatchLog". This may or may not contain any useful infomation.
If no solution reveals itself, you may want to file a bug report with Adobe: https://www.adobe.com/cfusion/mmform/index.cfm?name=wishform
Also, I'm wondering if there's another app in your arsenal that can handle this task. Doesn't Bridge (or Photoshop) have a batch processing feature?