Well, it's a little ridiculous; and probably unbelievable, but when I have more than five hundred lines of actionscript in tags in my MXML FLEX Main.mxml, all syntax highlighting, error and syntax verification, error reporting, "Problems" pane, and even sometimes compilation fail. Upon removing any chunk of code, it works again.
I don't see why Adobe could release a product such as Flash Builder 4.5 Premium, have this big of a problem; and nobody notice. Therefore I believe the problem has to do with my computer, or my project; as there's now ay more people have had this happen if I can't even find it on Google.
Additionally, many objects that have been defined in the MXML properties above the code, even those in All States, are now showing as warning: Access of undefined property down the side of my document. However, these warnings are not showing up in the "Problems pane", and aren't even yellow squigly underlining the right sections of code to pertain to the message.
Steps I have taken to TRY and fix this: I have tried restarting, as well as re-installing the IDE (Adobe Flash Builder 4.5). I have tried creating a new project. I have tried splitting my code into smaller .as files and including them. I have tried compiling my application.
Nothing has worked, PLEASE HELP.
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Edit 1: In response to the first answer, I have already tried increasing the memory allotted to Adobe Flash Builder 4.5 by editing the flashbuilder.ini and flashbuilderC.ini files in the main installation folder, it did not help; as my heap (heap display in bottom right) never uses more than 128MB anyways (even during compile) this did not fix anything.