A Google Webmaster Help thread reports that several webmasters trying to use the reconsideration form are experiencing significant difficulties.
As the user types in the box, explaining why their site should be reincluded in the Google index, the web page freezes and they get booted out. The issue seems to date back to July 26th, last Wednesday.
The issue was confirmed by Googler, Susan Moskwa on 7/28, saying, "thanks for letting us know, folks--we're looking into the issue." Then on Friday, Googler, Jonathan Simon chimed in saying, "We're still looking into this issue. In the mean time have you tried the potential workarounds that danielroofer suggests above?"
The form works fine for me, so maybe try deleting your cookies to see if that fixes things. If not, hopefully Google will figure it out.
Forum discussion at Google Webmaster Help.

Comments:
JohnMu
08/03/2009 12:31 pm
Hi Barry, a quick solution is to just use a different browser. It seems that some IE versions have a problem with the text-field on that page. Cheers, John
Barry Schwartz
08/03/2009 01:02 pm
Thanks John, so it is an IE issue with the form. Thanks for clarifying.
syn
08/03/2009 01:03 pm
my favorite workaround: make some noise!!! post your stats on your blog and twitter, make a claim why it's unfair and not true. write emails to every google contact you have in your inbox. beg them to forward this stat to your spam team. if you are really innocent (and i'm sure you are, arn't we all) you will get your penalty deleted in less than 2 days.... works every time. (at least in the cases where i was really innocent, they are not stupid the spam team, you know)
Satish
06/21/2011 05:04 am
You should read this thread at google webmaster forum on getting your site reconsidered. Its really amazing. Just read through the full text. http://www.google.co.uk/support/forum/p/Webmasters/thread?tid=2a7e8ceb32cf3f25&hl=en