As of late, it appears that a lot of Bell Samsung Vibrant phones are having issues with their SD cards. The SD cards are dying to be more exact. This issue is experienced mostly by people who have hacked their phones with the "lag fix" for Galaxy S phones.
However, part of the problem may be Samsung's own inferior components. This comes from the fact that the issue is being experienced faster by the people who used the lag fix, but it's also being experience by those who haven't used it.
Some users are saying that even if they did use the lag fix, they shouldn't be blamed, because the "lag" shouldn't have existed in the first place, so there wouldn't be a need for a fix. Fortunately, it seems like you can still send your phone in for them to repair, so your phone can work well once again.
Via - AndroidCentral