This article is from the CD-Recordable FAQ, by Andy McFadden (email@example.com) with numerous contributions by others.
There's a couple of possibilities. One is that your data source can't keep
up with the CD-R; try using disc-at-once writing from a disc image with the
speed set to 1x. If it seems to be getting worse over time, you may just
need to defragment your hard drive.
If that fails, a number of people have discovered that the problem is a
faulty CD-R unit (similar behavior has been reported on Sony and HP units,
which have different mechanisms). You should try 1x writing from a fast
source and with different sets of data before contacting the manufacturer,
since they will likely tell you to do exactly that anyway.
Be sure that there aren't environmental factors creating difficulties.
CD-R units are usually built to handle small shocks, but having a set of
speakers playing loud music on the same table as a CD-R may cause it to
skip, resulting in a failed write. Sonic booms, heavy construction
equipment, and nuclear detonations may have similar effects.
It's also possible that you simply have a bad batch of media. Try a
different type and brand of disc. Some distributors (e.g. dataDisc) will
exchange media that's provably defective.
Be careful with Advanced Power Management functions on some PCs. If the
keyboard and IDE devices are completely idle, the system may decide that
nothing is going on and switch to a low-power mode. Ditto for screen
savers that kick in after the system has been idle for a certain period.