That was it, thanks!
It seems changing the debug setting clears the cache by itself, so I didn't even have to do it myself. With RenderOptimizeMeshVertexCache set to FALSE, the piece of clothing rezzes; if I set it back to TRUE, it doesn't anymore.
Are there any drawbacks if I keep this setting to FALSE? Like, mesh taking more time to rez (with my slow connection, it's already hardly bearable, I wouldn't want to make it worse just for a piece of clothing...).
Thank you!