This is easy to fix, in the outliner, set it to display all nodes, down the very bottom of your list, will be some "unknown" nodes.
you should be able to save now.
Unknown nodes are created from nodes that require a plugin, if you have a special plugin loaded, save your file and open it on a computer that doesnt have the plugin, all the nodes that are related to that plug, become these unknown nodes.
"They had the name of my original fie, but in the extension it said .mb(then just random letters)"
these files are wha maya names its temp file, as it saves a new copy of the file, then once the save is good, it deletes the old file and renames its temp file.
If you have a pile of these in a dir, it because of your multiple failed save attempts. You can delete these.
"says un-recognizable file type"
because the file hasnt save correctly, you loose your maya binary file, it will never open.
This is why in production we prefer .ma's, because if the files doesnt save correctly, you can recover it, or merge it with an older version, so you dont completely lose all your work.
Since it happen sporatilly i think you are getting some sort of memory leak or something when your saving.
As soon as the first instance of this happens, restart maya.
And as soon as you can , remove the "unknown" nodes and save out a .ma, this is much easier to debug the scene file in a text editor.
Hope this helps.