Could you post more details on what is happening and when, also under what OS?
I think I have found what the problem was. When compiling, I was running 'make' instead of 'mingw32-make'. Not sure if it is only coincidence or not, but when using that, MAME appears to run fine again.
But to let you know, I am running Win XP (SP1 as I don't really need all the security stuff introduced in SP2 for a standalone MAME box - in my opinion anyway). What would happen is that the game would load fine. When pressing keys for credits, start, going to the config menu, etc nothing would happen for 10 or more seconds. Eventually an occasional keypress from earlier would then register and sometimes quite a few would all happen at once and then it would go back to delayed responses again.
So, all seems fine now. I have my skip_warnings and fast/skip_startup_frames working with all key presses registering as they should
