I have X3 and a version of LXI Expert that is about 7 years old ....can't remember the version number right offhand. I Copy from Corel X3 and paste in LXI and it works fine for me .....also worked with Corel 8, 9, 10, 11, and 12. However, copy and paste does not work well going in the other direction....from LXI to Corel.
In any case, if you export from Corel as encapsulated postscript, then LXI should be able to import as .eps. I believe in LXI the import command is called "merge". Try opening a new page in LXI and then merge the file you exported from Corel X3. Maybe not the answer, but it's worth a shot.