This is what comes from using Excel as a relational database, I fear.
The screenshot isn't quite legible enough for me to make out the layout. Assuming it's something like
x1, x2, x3 ... x16284
1,2,3...
786,787,788, ...
14282,14383,14384
...
There's not much that can be done in R without turning summersaults with one-and-a-half gainers. If the number of extra row breaks were consistent, what I could do is write a script in sed, ruby,python, etc., to join the lines.
If that's not on the table, try dividing the Excel table into bite size chunks to be cbind glued.
If, however, the longish rows are just wrapping and divided by newlines (\n), what is the problem that you are seeing on import?