Apps won't run on my Symbian smartphone! Help?

It sounds like your phone memory (drive C) is full and the apps have no room to create their temporary files. You need to clean that memory out, e.g. by reinstalling all the apps and selecting memory card as target.

So, make sure to have a memory card on the phone, as big as possible. Then go through all the apps and check their settings, make sure that they store the data on the memory card instead of the internal drive C. Especially so for the Messaging app if you use email and apps such as podcasting. Ovi Store also has a setting that tells that all the apps should be installed on drive E (memory card), the place where you should be careful to install all your apps, always.