The World's Fair

Example 1: It was difficult to get motivated knowing that both Season 9 of Friends and Season 4 of Felicity came out on DVD at the same time.
This particular excuse would be completely ineffective. The review panel would need to be told that Season 9 of Friends is where Joey and Rachel almost get together and that Season 4 of Felicity is where Felicity finally graduates and decides on whether she loves Noel or Ben.

Example 2: I've been mentally drained - thinking about the Avian Flu Virus has given me a serious case of the heebie-jeebies.
Scientific grant reviewers are generally very visceral personalities and as such will only commiserate with you if your fears are more visually arresting. Avian Flu Virus, whilst good, is still only capable of conjuring images of waterfowl - not the most scary thing to think about. A good point of reference of what might be considered an effective fear, is to ask yourself whether it would also make a good name for a professional wrestler. For bonus effect, you can even throw in the odd wrestling term. i.e." I'm mentally drained - thinking about Mad Cow has given me a serious case of the Hammerlock Superplex."

Example 3: My (insert name of high tech equipment) has a problem with its (insert copious amount of jargon terminology here) with frustrating results.
This type of statement is much too specific. As a past grant reviewer, my first train of thought would be to shoot back and query why it wasn't fixed given the problem is so clearly laid out. It is much more effective to use descriptions that are generally very vague in design. Try, "But this one goes to eleven."

Example 4: I sort of got sidetracked, but I have published a few things at McSweeney's.
Nice try, but this angle of reasoning would only work if the layman publication you refer to, is a favourite amongst scientists. If you're going to name drop, you should instead try the New Yorker, Harpers, or Maxim.

Example 5: Results were tough to come by because none of my colleagues wanted to collaborate with me anymore.
This particular excuse immediately informs the review panel that you suffer from low self- esteem. This is an incredibly dangerous precedent to set, since scientific reviewers are particularly well known for uppercutting (see how effective wrestling terms are?) individuals when they're already down. What would work better is to also provide an explanation that clearly suggests that you are not to blame for this unfortunate reality. In fact what would work best, is to blame Bush. For instance, note the following:

"Results were tough to come by because none of my colleagues wanted to collaborate with me anymore. They had recently got their immigration papers and have since all moved to Canada. This is a result of feeling stifled by the religious right wing agenda that President Bush so strongly favours."

or simply,

"Results were tough to come by because none of my colleagues wanted to collaborate with me anymore, because of Bush."

Example 6: Has a year seriously gone by already?
Feigning absent mindedness is very very risky. I've only seen this work once, and that was only because the scientist cleverly (accidently?) sent in a love letter written in a foreign language for review.

Example 7: And it would've worked too, if it wasn't for those pesky kids.
Actually, this one might fly. Scooby Doo is truly magical in scientific circles, but, please, you didn't hear that from me.