Sadly all GDI+ commands are always "out of memory" or "invalid parameter" so the messages doesn't really help figuring out what is wrong.
One thing that can normally cause this is an image that GDI+ cannot process (maybe because it is corrupt, too big, or in a format GDI+ doesn't understand). Do you have any images in the files you are exporting? If so, are the same images used in debug and release?
Is there any difference between you code in debug and release? (some $IFDEF somewhere, or different data?) Because there shouldn't be any difference between both.
Also, are you generating xls only, or also pdf? Normally this error should happen when rendering a file (to pdf, html, etc), but not that much when generating xls/x files.
If the code is not too big, can you try commenting out parts of it until it doesn't crash in release so we can get a better idea of what is causing the crash? Start with anything doing graphics work since this is a GDI+ error: Adding images, autosizing columns, etc.