Yipppppeeeeee - a bright moment today!
Last night SP 5.0 came out as EV. One of the changes is a new system setting under Assemblies that allows you to check a box for "Prompt before changing mate alignments on edit."
The way it now works is that if you have that box checked, then when in the situation when it would (undesirably) flip a bunch of mates for you, instead you get a dialog box that says This change will cause mate errors or warnings. Do you want SolidWorks to change mate alignments to avoid these problems?" and actually has a Yes & No button. Clicking the No button then effects your change and the tree lights up, thereby allowing you to fix the one other mate that you know is causing the problem, rather than it flipping
20 other mates that you don't want changed. If you click the Yes button, then it will go ahead and flip all the other mates that it wants to do, whether you deem them necessary or not, and then you get the old dialog box that just asks if you would like to view those mates.If you uncheck the option under assemblies, then you don't get the new first prompt and it's still the same as people have come to hate. Hopefully this will put an end to that nonsense.
WT