Yes it is BUT the only brokers trading it are the ones that don't use the DTCC as their clearing house...everyone else has been stopped dead in their tracks.
And look, I'm just trying to be informative here and the truth is that the DTCC suspended CLDR as of 2/3/11.
And if you want a prime example of how many shares can continue to trade after a DTCC Global lock down, check out SPNG...Over 200 Million shares have traded since their DTCC suspension initiated on 6/2/2010 while investors were on lock down.
If you are one of the lucky ones that have your stock with a brokerage house that does not use the DTCC great, buy & sell away, otherwise you are in limbo land until the suspension is lifted.
Now, as to why this was done, only the DTCC and the company can answer to that.