Analysis.

(Remember: this analysis is particularly true about British language and culture, though mostly it is the same for other English-speaking countries like Australia and the United States.)

Sentence by Sentence analysis.

Sally: "Solar power, eh?"
(This is an expression of interest. The use of "eh?" makes the statement an invitation for a discussion. Without this the statement can imply disappointment or incredulity ("Oh look what the idoiot has done now"). But by making a question, Sally is being neutral.)

Ivan: "Well, why not? What's wrong with a Solar Power company?"
(This is a very defensive answer. Notice that Ivan twice challenges Sally to give any objections she might have. He thinks that Sally is negative about the idea, though Sally has not indicated this in her opening words.)

Sally: "No, nothing, nothing at all. I was just interested to see what you had chosen. I'm not saying it's a bad idea. Just interested, that's all."
(Sally is surprised by Ivan's aggressive response. She says there is nothing wrong with the idea, and repeats "nothing" twice, the second time with the emphasiser "at all". She says explicitly that she does not think it is a bad idea, and says twice that she was only interested. This repitition is intended to calm Ivan down, and show that she does not intend to criticise.)

Ivan: "I went through a whole list of companies before I chose this one. It has a lot going for it. I think it will perform well."
(Ivan is still being defensive, but less so. He explains that he searched carefully to find this company (it's not selected by chance), and he thinks there are good reasons for buying shares ("it's got a lot going for it").)

Sally: "Ok, tell me about it."
(Sally takes Ivan's comment as an invitation to talk, although this was not really what Ivan intended. )

Ivan: "Right, first of all, I'm not a scientist, but I checked up on their stuff in the academic papers. The people who are scientists are impressed by their work. That's good enough for me."
(Ivan is trying to think of any criticisms that Sally will have, and is trying to show that he has thought of them. He starts by defending the scientists work. "That's good enough for me" suggests it should also be enough for Sally.)

Sally: "Not all academics make good businessmen though."
(The tone of voice is very important here. Ivan must see this as a contribution to a discussion, not as a criticism. )

Ivan: "I know that. I thought of that too. But they have a venture capital company handling their management, and they aren't going to allow the scientists to do anything stupid."
(Ivan is still rather defensive. "I know that" is not really necessary here, but Ivan is emphasising that he has thgought about this too. Notice the change in the subject of the pronoun "they" from referring to the scientists to referring to the venture capitalists. This is allowed in spoken English, but it is bad style.)

Sally: "I see that have a professional manager handling their operations too."
(Here Sally is looking for positive things to say. She has noticed that Ivan thinks that even neutral comments are criticisms. )

Ivan: "Exactly. And yes, I checked on him too. He used to work for Behrens Technology before they head-hunted him. He knows his stuff."
(Ivan is still being defensive, even when Sally is being encouraging. He keeps trying to think of places where she can criticise. That's why he says "Yes, I checked on him too" - he is answering a criticism that Sally did not make, but he thinbks she might.)

Sally: "How much are you going in for?"
(This question means "how much money do you want to invest in this company?" "Going in for" suggests that there is some amount of risk.)

Ivan: "I don't know yet. I think they will do well, but it's a long-term investment. It depends if I can find something to give a bit of sparkle to my results in the immediate future. If I can I'll take quite a big stake."
(This answer is neutral, not defensive. Ivan says he thinks the company will make a lot of money for him, but it will take a long time. He needs something that will give him some money quickly too, so he can't spend all his investment on Xsolaris.)

Sally: "Well, I might be able to help you with that, if you ask nicely."
(Sally is thinking of a company which can give Ivan a quick profit. But she is a little bit angry because he has been so defensive before, so she tells him that she will help only if he is more friendly. She says it as a joke, ("if you ask nicely" but it isn't really.)

Ivan: "If it's good, I'll buy you lunch - how's that?"
(This is almost an apology. Ivan is not going to do what Sally wants, and ask nicely, but he makes another offer, which will make their relationship more like that of friends and not just people who work together. It shows that he understands that Sally does want to be friendly.)

Summary

Ivan is not sure if he is doing the right thing, and he is worried and uncertain. He thinks people will criticise what he is doing. Sally does not want to be critical, but because Ivan is expecting people to tell him he is doing the wrong thing, he thinks almost everything that people say to him is negative, even when they don't want it to be. Sally tries to show that she is only interested, but when Ivan keeps treating her interest as unfriendly, she gets a little bit angry. But by then Ivan has realised that Sally doesn't think he is being stupid, and he starts to treat her more like a friend.