I'm getting the error in the title occasionally from a process the parses lots of XML files.

The files themselves seem OK, and running the process again on the same files that generated the error works just fine.

The exception occurs on a call to XMLReader.parse(InputStream is)

Could this be a bug in the parser (I use piccolo)? Or is it something about how I open the file stream?

No multithreading is involved.

Piccolo seemed like a good idea at the time, but I don't really have a good excuse for using it. I will to try to switch to the default SAX parser and see if that helps.

Update: It didn't help, and I found that Piccolo is considerably faster for some of the workloads, so I went back.