One way to avoid this in the future is to use the VI found here:
<VI.lib>\Utility\libraryn.llb\Is Name Multiplatform.vi
This VI will check to see if a file name is valid or not, and will provide a name that is valid. I tend to use this anytime I have a file or folder being made from a string control that the user controls (like a serial number that may be in the file name).