If you're working with mxm files downloaded from the mxmgallery, some of them may have problems with finding the textures used in them, depending on how the user packed them. Before importing them into Maya, or using them in Studio. Double click the mxm so it opens in MXED and it will tell you if it can't find any of the textures. Locate the textures included in the download when MXEd asks you to locate them, then press the Save and Close button in MXED. Now you can use these materials and you won't get any texture errors.
Or, after downloading a material, move the texture included in the package in the same folder as the mxm. Open the mxm in MXED again just to make sure you don't get any erorrs.
Or, move the textures to your usual texture folder, open the mxm in MXED and locate the textures, save the mxm.
About the Low priority, what do you mean by 'gets stuck'?