A good start would be to look at the book of Genesis, as this way I can go ahead and topple the foundation of the Abrahamic religions. God created a paradise for Adam and Eve. But as we all know, Eve took fruit from the tree of knowledge and shared it with Adam. What I'm interested in is the next bit.
Then the man and his wife heard the sound of the Lord God as he was walking in the garden in the cool of the day, and they hid from the Lord God among the trees of the garden. But the Lord God called to man, "Where are you?"
Wait, "Where are you?" did god just loose his omniscience? I actually envision this quite like our ancient brethren probably once saw it, a giant man walking through the garden to make sure everything was alright, the only way humanity knew how, by looking.
But the bronze age ruminations of how the 'beginning' occurred aside, there is still a very big problem with omniscience. When god supposedly created Adam in the garden, god was also knowledgeable about his future acts. Where in lies the quandary, why would god create a being in its own image and then see it do the one thing you told him not to do. With omniscience, god would have been able to see the result of any and all actions and the paths they lead out. This means god willingly created a being to go against gods own will. Adam didn't really have a choice in this as god being all omniscient, foresees the fall of man and allows it to happen.
Why would an all knowing deity create something that is going to fall? There is no logical way for an omniscient being to create something and not know the path it will follow. Some say god gave us free will. But to be omniscient god would have to know all possible paths and the likelihood of those paths occurring. Which, from the persons perspective, seems like free will, but to the omniscient being, it is all just moving along a play that was set at the moment of creation.
Take things a step further and add in the key part of Christianity. God must have planned this move from the beginning, meaning man was destined to fall and all those years or torment were not because god was angry, but god just planned it that way. This is where things get messy. You have the Trinitarians who hold that Jesus was an aspect of god. In this case, you have god, sacrificing himself to himself for something he had created to act out in a way that made man fallible.
But if you are Non-Trinitarian then Jesus was a very specific sacrifice for humanities' sins. In this case Christ was supposed to be part deity, thus making his sacrifice to be the final human sacrifice to god. Instead of being there on the cross, god is represented by this human deity hybrid? Was This really the best way to close the Adam loop hole? Omniscience finds itself unable to cope with this.
The difference is minor between Trinitarian and Non-Trinitarian, yet the conclusion is still the same, Omniscience does not work.
But what about Islam? Wouldn't god have seen the split between Shia and Sunni Islam? Would not god, or Allah if you prefer, foresee the split where one group tries to make Abu Bakr as the proper Caliph and the other sees Ali as the continuation of the family and therefor the rightful descendant of the Prophet. With gods Omniscience god would have foreseen the split and therefor made things clearer as to who would rule.
Omniscience is a deities worst enemy, unless of course that deity is more of a dick than anything. If god was just going for the most screwed up way to trash its creation, then yes, it would make sense...in a terrifying sort of way.