default bucket freezed when full

Created an attachment (id=766)
diag of node A

Install ns 1.6.0beta4-63 on 2 windows 7 67 bit.
On node A, create 4 buckets (2 membase and 2 memcached).
Load data to all buckets.
Default bucket on node A is 1/3 full of data (about 1.5 GB)
Run memslap on node A. At node A, add node B to node A.
Rebalance. Work as expected.
Then default bucket get full and memslap got error of out of memory.
Stop memslap. After about 30 minutes, default bucket is still full.
Run memslap again, get error a2b out of memmory.
Stop memslap. Then I can see free storage of default bucket going up.
Some how the second run of memslap trigger the process of moving data out of default bucket.
http://screencast.com/t/tUaqjg6Gne
http://screencast.com/t/SIyp1Tfnnk