I have faced similar problems so I can help. But with the information provided it may not be feasible to debug further.
Can you use any OS specific tool (you can also start with the task manager) and check what is consuming the most CPU and Memory times respectively? We will need to solve this iteratively and hopefully arrive at a solution.
At this point of time it could be anything - a cpu heavy process, a resource conflict, a disk intensive i/o or just something that is paging/trashing heavily etc.
