This error occurs when there is insufficient space on the timeline to adjust the clip to the required length. In the example you have provided there is obviously anoher clip at 04:28 on your timeline. The figures in the error will vary dependent upon what is next in the timeline. The first figure refers to the maximum amount of time you can apply to the clip (remember that slowing a clip increases its duration). The second figure refers to the percentage figure you can apply to slow the clip down by.
When I try to slow down some clips I get a message saying, for example,
'The clip length should be less than or equal to 00:00:04.28 and the speed rate should be larger than or equal to 90.'
Obviously if you have no other clips to the right of the one you are slowing down, then you will never receive the error.
The fix to your problem is to move the offending clips further along the timeline, or delete them.
COMPAQ something or other with 500Gb Boot Disk, 1Tb external Firewire Disk, 4Gb Memory and a super duper sound card, 19" TFT Monitor etc etc etc
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