We have tried a number of the solutions that are floating about there on the internet but I’m afraid we have concluded that the only solution is to free up memory, and on the iPhone that means just one thing: delete stuff.
So, you are going to have to think long and hard about which applications and how many photos, albums and podcasts you really need to carry around with you. Every bit of space you clear will result in an immediate improvement in performance.
Please, please, please remember to perform a backup via iTunes before deleting anything.