Error msg: "Task Loader; 21:C1"

running 6.0.3 client on 6.0.3 server.a user is receiving the following error msg whenever opening their own mail db (on server) from the notes client at their own workstation.

Task Loader

21:C1

this is simply an annoyance and does not prohibit the user from continuing any task in notes at all.

as a developer tho, i’m curious about any ideas as to what this refers to? my searching so far has been exhausted.

many thanks in advance.