Having a 64GB microSD card might be the culprit, but bear with me here. I have a Samsung Galaxy SII via T-mobile, and despite seeing that the phone only supports up to 32GB microSD cards, I'd seen many reports online that it could support the 64GB cards without issue. Bought one on an Amazon sale (SanDisk Ultra 64GB SDXC, Class 10), formatted it in FAT32 using the phone, and dropped music in from my PC. Android lists the total space 59.64GB, which sounds right. Currently, when playing music, the phone will experience several problems, including: 1. Sluggish speeds in scrolling through songs on the playlist and using functions such as Next, Play, and Pause and Volume Up/Down. 2. Many songs not playing at all, despite being a recognized file format (mp3). 3. Songs and playlists appearing duplicated within the app, but not in fact being duplicate in true on the microSD card. 4. Songs that do play do not proceed automatically to then next song once it's over. I've used the stock Music Player app and Winamp, with the problems happening in both. For problem 1, I thought it just might be the app indexing all of the new songs, looking for album covers online, etc. I left the app alone for a few minutes to see if this resolved the issue, but it did not. My gut tells me that this is some kind of memory issue, and my first thought was "If it can't figure out where something is, or the app is somehow seeing double, then it's an allocation issue," which would point towards the 64GB capacity simply being too much. I also came across the idea of the cache being too small--stock is 128KB, and increasing this to 1024KB or 2048KB could improve playback. But I think if this were the case, all the music files would be recognized and play, but the playback would be stuttered and choppy. I haven't rooted my phone again to check this out yet. Another idea I had was changing the filesystem on the microSD card from FAT32 to ext4, but since FAT32's storage limit is greater than 64GB (I think it's 2TB or greater), then this shouldn't matter, but it may be worth a shot. Anyone have any ideas? Do I just need to format the card and return it to Amazon for a 32GB one, or perhaps try additional music players?