Though this probably isn't it, you could check your Wavelab temp file settings under:
options, preferences, file
Mine defaulted to the c drive which didn't have the kind of space required for giant audio files.
Next step would be to follow the direction of the folks on laptop tapers who suggested you use some utilities for stripping / repairing headers. I just had to do this to a file that got messed up when I lost power while recording (actually, my UA-5 lost power and caused the pc to spontaneously reboot while recording, but that's another story). I'm also having major hassles using cool edit pro to open up large files when they have the headers. Even when cool edit is used to save the file, it crashes when I try to re-open it. Strip the headers and open as raw pcm and it works. fucked up... So if you're recording large files or 24 bit files, it appears that these utilities might get regular use.
david