What's the difference between "to suspect someone" vs "to be suspicious of someone"?
For example, what's the difference between these two sentences:
I'm sorry for suspecting you.
I'm sorry for being suspicious of you.
In many contexts, both forms mean exactly the same. But I think #1 would occur more often.
Another specific example of a difference; suppose you download and install updated video driver software on your computer, after which your computer keeps going wrong...
Given the identical Latin root, there's little reason for there to be a difference. In practice, using the term suspect implies they may have been responsible for something, whereas suspicious behaviour is less focussed. The term 'suspect' has certain legal implications, so the first might be seen as slightly stronger.
But that's a minor quibble - they're basically the same.