yaGTD does not appear to do any locking of the todo file. That means multiple copies can be running at the same time, and overwrite each other's changes.

yaGTD also does not appear to pick up on any external changes made to the todo file (for instance, by another copy of yagtd that's running).

Proposed solution:

a) only allow one copy of yaGTD to start up with the same todo file by using file locking.

b) test for changes to the todo file before saving, and refuse to write the todo file and save as another file if the todo file is found to be changed.