I have had this problem when using 1.4b on Win 98 SE. This fix usually must be performed over and over again, as the problem regenerates after a few uses of the software. If you're willing to give it a try, here's a possible fix that worked for me. Remember to back up any important files and use this method at your own discretion.

(1) Uninstall all version of LimeWire.
(2) Browse c:\program files to find the possible existence of a left over LimeWire folder or folders. Delete it or them.
(3) Perform 3 searches (F3 key) for files called lime, wire, and limewire. Use discretion when deleting any of these. You can mess up Windows pretty bad. NOTE: If you make a mistake and your computer acts wacky after deleting incorrect files, you can revert the changes made to your system if you are running Win98. Restart the computer in dos, type in "scanreg" click ok through the intro dialogues. Say "View Backups" choose a date that corresponds to a point in time before you made these changes to your computer. Restore it and restart.
(4) Install LimeWire 1.4b again.

This should fix the problem of the error message popping up at startup, but you might have an error message at the end. Ignore it and use the software until you can't start it up anymore. Repeat this cycle, and things should be ok. Hope this helped! :-)