Brailler
There are six dots in a Braille cell. Each dot can be either
raised or left blank. A black dot is raised on the paper so you can
feel it (circles represent dots that have not been used). A quick
calculation should tell you that there are $2^6$ possible
arrangements of the six dots. However, some would be difficult to
tell apart if you were blind and so no two letters use the same
arrangements placed in slightly different positions, for example
the letter "d" is represented in the following way: 
Here is the Braille alphabet:
Unfortunately something has gone wrong with the machine I use to produce Braille messages and one of the pins that makes a raised dot is not working. I typed a short message in Braille on my faulty machine. Can you work out what it really says:
The technician came to repair the machine and after she left it was worse than ever (a common story). Now my Braille machine randomly selects one pin that does not work. Can you decipher the following message written on the machine:
In the first part of the question, you can start by narrowing down the broken pin to one of only two possibilities.
There is a clue to the second part in the question
This was a popular problem that was answered correctly by many of you. The messages say "HELP ME" and "BROKEN".
Mathew Ladley from Saddleworth School reasoned as follows:
"For the first answer I narrowed down the possibilities of the broken pin - either the bottom right or the middle right one (since these hadn't been used). So then I just worked out what letter each symbol could possibly be, and worked it out from there..."
Ben Goulding from Whitgift School added:
"The dot on the middle right is not working. Some letters do not need this dot so do not get caught out."
Catherine Y and Yi Jean C from North London Collegiate decoded the second message as follows:
"We made a list of possible letters for each symbol, allowing either no mistakes or 1 mistake. We got a list as follows:
First letter could be: BFHL
Second letter could be: NORZ
Third letter could be: NORZ
Fourth letter could be: KLMOU
Fifth letter could be: DEHO
Sixth letter could be: MNPX
From here, we tried to make words:
The first two letters could either be Bo, Fo, Ho, Br or Lo.
We just tried various words until we got to BROKEN!!!"
You need to work systematically.
A chance to learn a little bit about Braille.
This site is an excellent resource: The National Federation of the Blind