I'm a little rusty but in 3DS Max 8 there is a section called tools or something over on the far upper right tabs. One of the tools in there can fix this issue but I cannot recall which one.
So to avoid this from happening when you scale an object; scale the entire object or scale the two parallel sides together. If you scale just one side by itself this will happen. Wish I could give a better example but I have not done a map in awhile. My one big issue with Windows 8 was that it does not like my copy of 3DS Max 8.
We have many example source files in Max format you can learn from, I suggest checking out our [DATA] H2MT - The Essential Collection
. It is large but makes H2PC mapping much easier.