When I'm really really stuck, I generally stress out that I should be able to figure it out so I walk outside, sit down, listen to relaxing music and imagine I'm on some isolated mountain somewhere away from all the problems of deadlines and managers and algorithms...then i just write down what i need to do and what i have done already and have a little brainstorm session with myself over possible causes/solutions from sensible to crazy, just anything possible... generally I always come to 2 methods - divide and conquer and document and destroy (the latter being used in cases such as having to fix something in an undocumented 10,000s lines long sproc that someone who left the company wrote)