PLease be aware that the latest wine versions don't work anymore because they stopped using the mozilla activex pluging and made their own gecko version which doesn't seem to work with winmx.
Any version up to 0.9.16 is fine, versions 17,18,and 0.9.19 don't work - at least not for me.
That error shouldn't be critical though, as it only affects the update bar (I think), so maybe someone can look at it and figure out how to get it to work anyway....