The following is not legal advice. Please consult a qualified immigration lawyer to discuss your specific situation.
As I have been writing for a few days now, USCIS filing fees will increase on July 30, 2007. However, the filing fees for EB cases that were current per the July Visa Bulletin will be accepted through August 17, 2007. When filing other applications with the I-485, it is recommended that separate filing fee checks be used for each application.
Why? Because if there is a mistake with the fee amount enclosed, or with a missing signature etc., the USCIS will return only the application with the incorrect fee. For example, if you apply for Employment Authorization with your I-485 Adjustment Application and you enclose separate checks for each, if there is a mistake with the Employment Authorization Application, only that form should be returned and your I-485 application should remain safely filed. On the other hand, if you submit only one check for the incorrect amount, the whole package will be returned, probably after the August 17th deadline, and you may be in for a very long wait before you can file again.