I don't think this is a server issue as I think I get the same problem in single player. Items won't pick up, or remain stuck to the mouse pointer. Also some craft actions go off twice.

IMO the mouse control in vanilla wasn't great but Tekkit seems to be getting worse or having bad days, yet if its happening in single player it can't be a network or server issue can it?

I have reinstalled not so long ago in an attempt to fix a "can't log in" issue, and I lost all my waypoints as a result. Don't want that again.

Also I found that single player create mode FPS sucked, yet survival was OK. Don't know if maybe it was the biome, create mode started in Jungle?

No idea about mouse. Mine has done the double right click thing many times. Seems to stop again after a while though.

Just wanted to mention the 'can't log in' error. The solution to this is to change your minecraft password. Even if you change it to the same thing as what it currently is, just go through the steps on minecraft.net

No idea what's going on with that, but hey.

In my case it turned out that minecraft.net was "down".

You might have something with the password idea though, sometimes I get kicked out at login and get "server unreachable" for a short while afterwards like maybe it was a lock out time to prevent dictionary attacks.

Your mouse buttons are just getting worn out, there's little you can do besides sending it in/replacing the switches yourself.

Mouse is fine in everything else. I haven't checked vanilla MC yet.

Sometimes double pressing the alt key works. Sometimes quitting and relaunching tekkit works. Sometimes I download a fresh copy of the lwjgl from sourceforge. I have a small shell script for that (linux) but I expect it's similar on windows.

Actually I am starting to suspect the mouse now as I realised the highlight function was a bit odd. Turns out it works better if I press the touchpad's left button instead.

On the bright side it was only a cheap ASDA value mouse.

The cheap ones don't last that long - I bought a cheap-ish wifi mouse for my laptop ... it was useless within a few weeks (cursor jumping all over the place on screen, or moving on it's own). Bought a better one - no problems since

Tried a drop of WD40 on the left hand switch. So far so good.

The case came apart without breaking, otherwise I'd have had to use duck tape as well.