On Linux systems some window managers make it difficult for apps to place their own windows, insisting instead on using OS settings to manage them. This is most evident when using the OS' "Smart" window placement options ( in Ubuntu per Unity Tweak, gconf, or Compiz Config), but at times most other settings also yield unpredictable results.
This has been confirmed by the core dev team:
http://quality.runrev.com/show_bug.cgi?id=14313
As a workaround you can set the loc twice, once on preOpenStack and again on openStack after the window manager has rendered the window. In some cases this may result in the window jumping into position, but may be more desirable than not having it in its designation location at all.
If you're seeing this on anything other than Linux please note your OS version so we can explore this further.