apps not installing on my galaxy mini

Hi guys, I am totally new to this forum. so please help me out. I have a Galaxy mini s5570 phone with froyo 2.2. Its Warranty of 1 yr has expired in last month. It was working quite well. and installed any app that supported froyo. but now there is a wierd problem happening with it. Let me explain it throughly.
few days ago, I downloaded Painkiller apk game of around 32mb. I tried Installing it. But a msg popped out 'app not installed'. first I thought its incompatible. so i installed it on another phone with same firmware. and to my disappointment, it installed.
then I thought there must be memory issue. so i backed up and emptied most of my storage both sd & phone memory. but it still wont install. Disappointed, I tried reinstalling my backed up apps and now they are also refusing to reinstall!!! please help me out. Is it a firmware or corrupt sd card?

 

Thanks for reply man, but clearing data/cache is not helping. I dont know whats with play store. but apps on my sd card which I had backed up using a backup app, are not restoring. same msg 'app not installed' :-|

 

Update..
anyone who has same problem and stumbled in this thread, I got a solution after google search. its that annoying 'smdl2tmp1' file causing problem. This happens when sd card is fullfilled. it blocks all installations. this file is normally located in /sdcard/.android_secure. Go and delete it. (This file is not visible in mobile phone. so you may want to connect to pc in storage mode.) thats all!!!!!!