I wrote too much below, so I wanted to give you the opportunity to see precisely the issue without requiring additional reading.
When dragging and dropping more than one PNG into Construct 2 simultaneously, the PNG graphics, while appearing to be only one of the dropped graphics, will infact contain all dropped graphics in a single entity. This is the case in Windows 7 SP1 with updated HD Radeon graphics driver via Catalyst Control Center.
The resulting entity(noted above), when made to appear via actions ingame, changes from one dropped PNG image to another.
See included PNGs to observe resulting PNG from simultaneous drag-drop.
Public Dropbox PNGs
And now, my initial message.
I finished my first tutorial with your program, which I am loving thus far. To sidetrack just a moment, I just wanted to mention that I was distraught by the belief that no tool existed that could allow me to create games for different platforms in a manner not dissimilar to that of starcraft broodwar's map editor, which I enjoyed very much for creating UMS maps. Basically, a user friendly code input UI for games/apps, without requiring actual code. This appears to be it, and I'm very grateful.
Alright, so onto the bug. Apologies if such a statement does more to waste your time than to commend your work.
I created the ghost shooter game, and couldn't understand why my bullets would fire correctly, only to morph into an explosion, followed by a monster, followed by a player graphic, all while in flight and killing monsters with explosion graphic registering upon contact of monster.
So I reread the tutorial, checked my triggers, and did so again. I was perplexed. So I exported my file to public dropbox, intending to send it to you for review.
Upon opening the images folder (as seen in attached .jpg), I saw that the "bullet" graphic was depicted including the other 3 graphics next to it. I immediately realized, and thereafter confirmed, that this was causing my odd bullet-morphing behavior.
I also immediately realized and thereafter confirmed that this was caused by me attempting to drag and drop all 4 PNGs onto the Construct 2 editing surface at once. When I did this, I was confused that only the bullet was successfully transferred onto my layer, and proceeded to drag and drop the others one by one.
The bullet graphic that inadvertently included all 4 graphics appeared only as the bullet within Construct 2, masking the bug.