I use a Nokia Asha 501 touchscreen phone which I bought January this year. Originally, it contained several apps, Nokia store, Gifts and Games amongst other amazing stuff plus some follow-come pictures.
Just a few weeks after it was bought, I tried to connect it with a USB cord to a laptop to share some stuffs when the screen went blank and it switched off itself. I disconnected the USB cord and tried to put it on. The phone came up, but the background picture was wiped off. I tried to set it up again and then I discovered the whole pictures had been wiped off. I thought that was the least of my worries, when I discovered that all my pre-installed apps were all not working and all my authority certificates had been wiped off, together with all the follow-come apps from Nokia store, Gifts and Games. I tried to re-install the apps I had previously downloaded which were functional, but each time I tried, I got a message like "Error. The system doesn't recognise who is trying to authorise the app. Please contact your service provider to get this fixed.
C=US; O=Unified Testing Initiative (UTI); CN=GeoTrust CA for UTI". I've tried all I can to no avail. Now all my apps that I enjoyed before, I can access no more.
Please, I would really appreciate any help that can get my phone back in order.

*Help a desperate sis plzzz*

I think the phone needs flash. Take it to a repair center.

urhoboman: I think the phone needs flash. Take it to a repair center.

Ok...the phone is normal for other things like calls, sms, etc just that I cannot download and install any apps on it, even the default apps are gone too
I'll try a repair centre as you suggested. Thanks.