I have attached an example, with instructions, that demonstrates this bug.
Essentially, if I have a R# intellisense window and I type in an entire method name, including the open parenthesis, R# badly reformats the code that immediately follows.
In the attached example, I have this snippet:
I have R# configured to "Auto-popup after dot" with a delay of 0ms.
After typing .Append( (do not autocomplete it) after the builder token in the if() statement, R# reformats the code like this:
Clearly, builder.Append((1) is incorrect.
I also found, whilst putting the attached example together, that if the Foo() method has zero or one parameters then R# was likely to crash. (See RSRP-39788: http://www.jetbrains.net/jira/browse/RSRP-39788 )