A user has a PO in PO20, and they are doing the action of Issue Final on it to print it.  When this action is taken, the following error message is received:  "Message Not found (    /108)."  Has anyone else seen this before?  The version of our applications is 9.0.1 MSP 4. 

Can the end user print anything else in Lawson besides pdf's?

Yes, the user can print other things in Lawson.

Is the problem with all PO's or a specific one? Can anyone else print the PO? Make sure they have access to the invokes as they are needed to print. Also certain types can not be done through PO20 like EDI. - Just some ideas, it may be none of these but it is a good place to start.

It's actually just one specific PO. There were 7 other POs created that are just like it, and those POs printed just fine. No one else can print the PO.

Since it is just that PO, printing is not the issue. My guess is a data element is invalid and that may be hard to see from the portal page. I would dump the header and lines for that PO and make sure there isn't what I would call a funky character (non UTF-8). I've had this happen in uploads and the only way to see it was through a dump. If that isn't the case verify data like UOM's etc to make sure they are valid. Hope this helps.

Those funky characters are trouble makers.  If you don't find anything in the data dump take a look at the comments (line or header).  I've run into issues in the past when buyers copy emails into the comments section and those emails can contain funky characters.