Sources are suggesting that the ongoing degradation of the relationship between Apple and Adobe, once the best of friends, is about to get a whole lot uglier, as the latter prepares a lawsuit against the former.

Following Apple's move to change its iPhone SDK to ban the use of cross-platform compilers, which essentially banned Flash but also targeted Silverlight, C# and .NET, it seems that the relationship has now soured to such an extent that legal action is being planned.

For now, all Adobe will say is: "We are aware of the new SDK language and are looking into it. We continue to develop our Packager for iPhone OS technology, which we plan to debut in Flash CS5", but if you work in the legal department at Apple then don't be surprised if a big fat envelope arrives in the next couple of weeks.

We'll bring you more on the precise accusations being levelled as soon as we get it.