There can be many reasons for the same. Here are few issues:
1) You have reached your limit of Picasa Account.
2) Videos are not rendered or adhere the standards of Picasa.
3) Your Mobile Internet Service is not working.
4) Overall size of the video exceeds 1 GB.
But most likely it seems like an issue of standards. Please read the following to know more.
http://support.google.com/picasa/bin/answer.py?hl=en&answer=55990
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