The b2c2.dll error stems from the SkyStar2 Streamreader. It is unclear if this poses a security risk or not. As with any registry error, it is possible to cause major problems. At worst, it can cause Trojans, worms, spyware, and other malicious content. At best, it will slow down your computer and cause your computer to run at less than peak performance.
Running a registry cleaner will take care of this and other registry problems. Beware of registry cleaners that are not from a trusted source. Some less reputable companies flag non-existing problems to get you to buy their program. That is why I suggest ZookaWare PC Cleaner. They offer a 60-day money-back guarantee, and they are a member of the Better Business Bureau.