Why does Delphi 2009 sometimes (more often that not) insist I build?

I have noticed that with Delphi 2009, I often get strange errors when compiling, such as recursive unit use, and sometimes just (seemingly) random errors which point to white space at the end of a unit.

These are not really errors, because a full build will fix any of the pro开发者_高级运维blems, and I can carry on. I suspect that generics have something to do with this. Now a Delphi build is very fast, but this is still frustrating. Delphi 2006 and Delphi 2007 did not do this, but then they didn't have generics.

Hard to tell without more details, but I would suspect some kind of confusion in one of the paths the compiler relies on to find the pas/dcus. Depending what has to be compiled, the order of the units found is not the same, or even the units are not necessary the good ones.

Do you have any modified Delphi unit?
Do you have a separate folder for the dcus?
Do you mix the source and compiled units folders in the paths?