There is a pretty nasty bug in Magento if you are using multi store view with configurable products. I have recently patched it nicely with an extension that overrides the original controller method. This is a much nicer fix than actually hacking the core files which can then break in the next upgrade.
In any case, even with this fix, you will still want to double check if the next upgrade fixes this issue. If it does, you can simply disable this extension or delete it altogether. Otherwise, you may want to look for differences in the _initProductSave() protected method. This code is release as open source and free (Download here: Activo_Multistoreviewfix_0.1.0).
The original issue as it shows on the magento websites:
I hope this helps a few other magento developers out there…