This is with kernel 2.6.31.14.12 (shipped last week) and all updates applied.

Some (menu) operations are rather slow even if top still reports more than 100m free memory. E.g., it takes more than 10s until "User Settings" are ready to take input.

("User Settings", this is: System > Administration > Users and Groups.)

User login (from gdm) is also rather slow. Even console login takes approx 3s. It displays "Last login... Welcome to Ubuntu! nearly instantly, but then you must wait until the prompt appears.

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karl