Nokia Applications :: Book Reader On 5233?

I got a book reader from ovi store called 'Bubue' to read epub, text files. It worked beautifully for a while then every time i changed a book it started shutting down on me, I've tried reinstalling 3 times just now, it used to work but not anymore, jar ebooks are going blank after a minute. Also my device is getting slow in response. Games i downloaded, two of them got corrupted. one was Nokia game. Climate mission, i think it was called.I've already tried factory setting restoration, before that i had re installed phone but at that time I didn't have book reader.I have stored many books on my memory card, could that be reason for slow phone n corrupt games n application?. I have 8 gb memory card and im using almost 300 MB.59 mb off internal memory is free.