diff -r 4d9106153407 -r 545990c7a5e4 indra/llcharacter/llhandmotion.cpp
--- a/indra/llcharacter/llhandmotion.cpp	Thu Jun 21 16:44:04 2012 -0400
+++ b/indra/llcharacter/llhandmotion.cpp	Thu Jul 19 15:37:44 2012 +0200
@@ -132,16 +132,66 @@
 	{
 		if (mNewPose != HAND_POSE_RELAXED && mNewPose != mCurrentPose)
 		{
-			mCharacter->setVisualParamWeight(gHandPoseNames[mNewPose], 0.f);
+			// Only set param weight for poses other than
+			// default (HAND_POSE_SPREAD); HAND_POSE_SPREAD
+			// is not an animatable morph!
+			if (mNewPose != HAND_POSE_SPREAD)
+			{
+				mCharacter->setVisualParamWeight(gHandPoseNames[mNewPose], 0.f);
+			}
+
+			// Reset morph weight for current pose back to its
+			// full extend or it might be stuck somewhere in the middle if a
+			// pose is requested and the old pose is requested again shortly
+			// after while still blending to the other pose!
+			if (mCurrentPose != HAND_POSE_SPREAD)
+			{
+				mCharacter->setVisualParamWeight(gHandPoseNames[mCurrentPose], 1.f);
+			}
+
+			// Update visual params now if we won't blend
+			if (mCurrentPose == HAND_POSE_RELAXED)
+			{
+				mCharacter->updateVisualParams();
+			}
 		}
 		mNewPose = HAND_POSE_RELAXED;
 	}
 	else
 	{
-		// this is a new morph we didn't know about before
-		if (*requestedHandPose != mNewPose && mNewPose != mCurrentPose && mNewPose != HAND_POSE_SPREAD)
+		// Sometimes we seem to get garbage here, with poses that are out of bounds.
+		// Clamp requested pose before setting the new pose and request
+		// relaxed hand pose instead as default.
+		if (*requestedHandPose < 0 || *requestedHandPose >= NUM_HAND_POSES)
 		{
-			mCharacter->setVisualParamWeight(gHandPoseNames[mNewPose], 0.f);
+			llwarns << "Requested hand pose out of range. Using HAND_POSE_RELAXED." << llendl;
+			*requestedHandPose = HAND_POSE_RELAXED;
+		}
+
+		// This is a new morph we didn't know about before:
+		// Reset morph weight for both current and new pose
+		// back their starting values while still blending.
+		if (*requestedHandPose != mNewPose && mNewPose != mCurrentPose)
+		{
+			if (mNewPose != HAND_POSE_SPREAD)
+			{
+				mCharacter->setVisualParamWeight(gHandPoseNames[mNewPose], 0.f);
+			}
+
+			// Reset morph weight for current pose back to its full extend
+			// or it might be stuck somewhere in the middle if a pose is
+			// requested and the old pose is requested again shortly after
+			// while still blending to the other pose!
+			if (mCurrentPose != HAND_POSE_SPREAD)
+			{
+				mCharacter->setVisualParamWeight(gHandPoseNames[mCurrentPose], 1.f);
+			}
+
+			// Update visual params now if we won't blend
+			if (mCurrentPose == *requestedHandPose)
+			{
+				mCharacter->updateVisualParams();
+			}
 		}
 		mNewPose = *requestedHandPose;
 	}