PLease help with armature and posing!!!

Well i have a character created and rigged too… and one more character complete in another blend file… now i wana do something with them togther … so i used the append or link optioin and appended the 2 characters… now when i try to animate them… the problem is… like

i added two paths for both of them to walk… then created the actions required by the body and added key points… but the moment i convert these actions to NLA strip and change the drwoing man icon to strip icon… the armature jumps back to the oirgin and it just keeps changing if i even miss a single bone… which genrally shudnt happen… now is this a problem common when we append two file?? or shall we link the two… which is better??? and also i tried clearing the origin with ctrl-O … and all calcualted the bones role angle too… but nothing is helping… please help as iam stuck and its irritatting…

also when posing … when i try to copy the pose and paste a mirrorred position … its not working… even x-axins mirror option on and i try to extrude bone… dint help the mirrored bone come out extremely large and in some strange direction but not in the x-axis mirror… i dont uinderstand why is this happening suddenly.

i dont understand why its happening… its sometimes happeing with individual files too… the x-axis mirrored bones are not comin out rite when i try to rig somehting in a indvidual file…and all the above problems in idiviudal file too… why is it happeing out of the blue iam not understanding… please please please please tell me a way to correct it and get my way through!!

I tried out a demo on a new file and created a few boxes and try to animate the,… well same problem, is comin…even the envlope fuciton is not working … its only the vertex group… iam not uinderstanding wat happened to the software suddenly… i dint play around with any settings then why is it hapening??? what do i do to correct this pelease help… shall i re-intstall???

I can’t help from your descriptions but if you post the .blend I’ll (we’ll?) be able to sniff the problem.