benn600,
I have had the same problem. It is definitely the FLAC encoded files when selected quickly result in MC crashing. I have tried the same thing with APE/MP3 files with no similar result. Quickly selecting, playing, then selecting another and playing..etc...will eventually crash MC if they are FLAC files or going back and forth between MP3 and FLAC. Unfortunately, the pattern is hard to pin point. I have done it times where it took a long time of doing the above procedure to crash MC, other times it will be the first time I switch to a song. I want to say that it is great that SCTHOM made a plugin (Thanks!) since I would have been out of luck for several utilities that I like to use for music tagging, etc. that only support FLAC and not APE. I had used APE for a long time with no problems, but converted all of them to FLAC once SCTHOM made the plugin. Up to that point, there was NO support from MC on FLAC files.
Anyway. Some builds of the FLAC plugin seem to result in this issue more than others. I will say the later builds are much better. It used to crash consistently almost every time you did the above procedure after one or two songs. Later builds seem to be spotty on the crashing, but I can always crash MC at some point. This may be some weird interaction with various new builds of MC, which makes it harder to pinpoint the code that is at fault. The first 30 seconds or so seem to be the "danger" area where it is prone to crashing MC if it is a FLAC song and the next is selected. In pure "listening" mode where I listen to songs straight through to the next, I have never had it crash MC with FLAC files. However, if you are doing tagging of FLAC files /modifications of files within MC and are doing quick skips to the next song, it will eventually crash.
Once it crashes , it seems to result in very frequent crashes from that point until a reboot. If you have LAST.FM audioscrobbler plugin, this will result in more frequent crashing of MC with quick selections. Also, I have tried nuking the MC database and various other things and it still happens. Winamp seems to work fine with the same set of music files (flac/MP3 mix).
For me, I will stick with FLAC in MC, even though it can very annoying at times. Like you, I hope that at some point it will get resolved.