Ugawa,
I have 4 novels going right now, all in various stages, and a fifth rattling around in my head. The four I have begun are romance with the fifth being horror. I have problems of life interrupting my writing and quite often the problem is not writer's block but rather how to put my idea into words, having it make sense, and choosing the right words so that it doesn't sound like a 5 yr old writing it. That is my main problem then I lose my place in the storyline, being I write in linear progression. I am on page 33 right now and my brain automatically thinks of edits for what I've written. So I highlight, copy and paste to a new document for the edits unless a single word change or deletion. Then I have no problem. When motivation wanes I dream of the novel(s) and why I am writing them and who I write them for or who inspired them. Example: the novel I am writing now is for Eric Mabius, inspired by Alex O'Loughlin and his character in 'Moonlight' and my dreams and visions of Eric. They are precognitive and rather irritating and confusing. By writing this novel I hope to express my feelings about the dreams, visions and my affection for both men, also I am beginning to understand the feelings and emotions behind them. The meaning of them is not exactly face value and that is the meaning of a good book, you should see parallels between storyline and your life and feelings, and come tro understand them and yourself more than before you began it (reading or writing).
Motivation loss? do something else not related to reading or writing. Play a game (pc or otherwise). For me, the best destroyer of writer's block was the pc game "Phantasmagoria" because you had to solve puzzles. My WB was often a puzzle of how to write this or that. I solved the game's puzzle, then the storyline of the game became visible to me and thus my own puzzle was solved.
Hope this gives you ideas how to solve your problem.
Alana