I think that you have the spring connected properly, otherwise it would not have worked for several months prior to giving you this problem. I had a similar issue and it turned out to be the clutch master cylinder. The seals were bad. The best thing I did was get a Toyota master cylinder and replace it. I went through 2 of an off brand and they did not hold up.

Check for a part number here: http://www.toyodiy.com/
Then check an online Toy dealer or check your local to see what kind of a price they give you.

Bill Reid
'93 T100 SR5 4X4
'05 4Runner SR5 4x4 (wife's DD)