Bundle / Group Products Inventory Problems

We have problems with increasing the quantities of bundle and group products. ie, for a bundle product (lets call it Z) has one item X and one item Y. we have 100 of each X and Y in stock. however, we cannot add the bundle product Z. We are also facing similar problems with Group Products. We have installed several external modules; Purchase Module from Maison du Logiciel and Ajax cart pro from aheadWorks. They might be in conflict but we are not sure. Please respond with how you intend to investigate the issue and how you propose to solve. We are looking for Highly experience coders ONLY with extensive Magento modification and customization history.