Memory Card Problems on Nokia 5800

I hate when I am facing another memory card problems on my Nokia 5800
Yesterday after I installed another theme on my nokia 5800 and then I wanted to apply the new theme suddenly my phone was blank and restarting it self!!!
What an annoying things!!
I faced this problem (the phone restarting it self) many times!
And everytime it happened it was because of the memory card...
I don't know what is wrong with the included 8GB memory card?!
I couldn't find Nokia brand on it or even other brand.
Is it nokia original accesories or what?
The Quality is very bad and its driving me crazy when something wrong with it!
Now I bought 4GB San Disk MicroSD card for my Tube. I hope There won't be any problem with it!