You will need a charge only cable for most of the USB style chargers unless they are specifically made for a BlackBerry. Most generic or third party chargers are wired for Apple devices and do not have the proper connection on the data lines to signal the PlayBook that is is a charge source, not a low current usb port or a defective PC usb port. The new OS 7 phones also need this connection on the data lines to ensure they charge.
My suggestion is to get a charge cable or not buy a charger unless you can test it first in store or have a return policy. In other words, you may waste a lot of time trying and buying online.
Even ones that previously worked with the PlayBook can have changes in production and the one shipped to you may not be the same version as suggested on the forum. I had this happen when I ordered more of one that worked for me and the second set did not work. The vendor told me they were the same part number and said he would just ship some more and check the labeling more closely. The third set that came were different still, but worked. All had the same part number but were labeled slightly different and were wired slightly different. In my case, the ones that worked had both iPpad and Android P1000 ports. The second set only had iPad/iPhone labeled ports, the third had iPad and a iPhone/P1000 port. The P1000 port worked without the charge only cable with the phone and the PlayBook, but needed a charge only cable for the Playbook to draw more current.