Do you have TortoiseSVN installed? Version 1.7.15 of Tortoise, 1.7.18 of SVN (these are not the latest versions, because for Mendix you need an older version).
When you select the folder in Windows Explorer you can choose Tortoise SVN → Resolved … from the contect menu. After that the conflict should disappear from your modeler.
The folder “javascriptsource” is a new default Mendix folder since 7.22 or about. If you had it in 7.18 you can solve it as Diederik says.