Just like in topic, I'm trying to burn about 760 MB of files on this unusual medium. It used to work in "old" K3B version. Now I've got K3B 2.0.0 and it cannot recognize the size of the medium.
Is it regression or I have to configure something?

in k3b try: settings -> advanced settings -> allow over burn

I have marked this. It used to work in old versions - I mean KDE3 versions, but it's not working now.

in the burn window try changing "writing app" from "auto" to "cdrdao" (I think cdrecord is default)

Default option is "auto" so I don't know what K3B chooses. I've tried both cdrecord and cdrdao, none of which works.

since k3b just front ends these other programs I wouldn't think k3b is the problem unless it's calling the programs improperly. If the calls are wrong you could try calling cdrdao or cdrecord directly.

2 non-Kde things you could try
1) a diff burner (Nero or a gtk/gnome)
2) find and install cdrecord (instead of wodim/cdrkit), if you search cdrkit and cdrecord it will explain)

other things:
there is a k3b irc channel (low traffic)
you could post the the k3b mailing list or post a bug http://k3b.plainblack.com/support
is this you bug https://bugs.kde.org/show_bug.cgi?id=241534 ?

Today I've spent some time trying different things. None of them worked. Tried wodim and cdrdao from command line, then installed cdrecord from sources and still nothing. Wasted 5CDs.
Bug 241534 seems to be the case, but I'm using this 800MB CDR0M, so I don't know. I've added information to bug report. Let's wait.

As in the old K3b, the way to change the media setting is less than obvious. While you have a data project screen open, look at the bottom for something like "Available: 703.1 MiB of 703.1 MiB. Right click on that and there is a setting for 880 MiB/

not very obvious, would be nice if it was displayed as a button of sorts or in the burn window as a 4th tab

see bug https://bugs.kde.org/show_bug.cgi?id=144444, maybe post that you'd like it displayed differently

This option changes nothing. I think it's just to show user size of his compilation - nice thing by the way. I may choose 880 MB, input 800 MB, or read capacity from disk itself. Whatever I do I got the same result: insert bigger disk. Look like K3B checks disk size before burning and finds out there's ordinary CD.

when you file a bug report regarding a thread it's good to post the link here https://bugs.kde.org/show_bug.cgi?id=241534

Link added

k3b 2.0.1 has been released and bug 241534 is fixed (per announcement)
http://kamikazow.wordpress.com/2010/08/ ... -released/