I have used this tool before with no issues before. Maybe the information you are copying contains illegal characters or extra spaces? It does not do a ton of error trapping as it assumes the user knows exactly how to use it.
I have expanded on his tool and added paste capabilities to Sales, Payables distributions, and Intercompany+Multicurrency Manual JEs for free below if you are interested (with instructions):
Expanded Free GP Paste.
~James