I have a problem with my nokia n85. i bou...

i have a problem with my nokia n85. i bought it just 5 month ago.. when i want to turn on my phone, it just showing nokia n then it just keep repeating. can't continue to the menu.. but when i take out my memory card, it can continue to the menu. when my memory card is inserted, the phone loading is become slower than no memory card. yesterday i try to format my memory card. i think can be solved like that. but after i format my memory card,it just the same. my phone become slower, n when i want to turn on, with memory card inserted, it can't continue, like i say above.. so i want to ask, should i change my memory card? to get my phone back to normal. when i turn on my navy wheel, my phone can become slower too..why suddenly like this? but it's no problem, when i turn off. the important thing is about memory card.
thx