Everyone knows that managers are clueless. They set impossible deadlines, they can’t delegate properly, they keep changing priorities and so on. Google has 1.8 million pages when searching for clueless manager. Clearly there is a lot of cluelessness going on. In fact managers are so clueless that most nerds don’t bother waiting to see if you’ll turn out to be clueless or not - they simply flip the clueless bit as soon as you are introduced.
New manager’s manager: Hi everyone, this is Manager, your new manager.
Everyone: [Clueless. Another bloodly manager the last one was so clueless. This one looks the same.]
New Manager: Hi everyone, as NMM said I’m your new manager. I’m looking forward to working with you all and finding out how I can help.
Everyone: [Clueless. Just as I thought empty platitudes. Clueless]
Now since you are reading my blog you clearly aren’t clueless are you. 
Unfortunately, unless you are joining an extraordinary organisation the chances are that lots of people will assume a lack of capability based upon their experience with others. Of course given your boundless ability you’ll turn these people around. Eventually. Until then you’ll have to deal with the consequences.
People who assume you are clueless will be less likely to come to you for help. Why would they bother? You’ll have to work hard to discover when people need help and be careful to actually provide genuine help.
People will assume that you aren’t equipped to understand their nerd problems. Be prepared for lots of slow explanations about how computers work or what XML is. Worse, you’ll find that people will assume that you don’t care about quality and will sacrifice long-term benefits for short term “progress.
Good luck.