Some database problems could not be repaired

Hello Forum,

I have a number WordPress installed on my Yahoo-site http://www.passagenproject.com. Everything has been running just great for many years.
Now suddenly my main blog is not accessible. Yahoo staff has first been able to repair, but now they don’t want to help anymore. I tried to repair the database with WordPress database repair help, and got a report, that everything was o.k. besides wp-comments and wp options.
The WP message was:

“Some database problems could not be repaired. Please copy-and-paste the following list of errors to theWordPress support forums to get additional assistance.
wp_comments: 1 client is using or hasn’t closed the table properly
wp_options: Table is marked as crashed and last repair failed” Some database problems could not be repaired. Please copy-and-paste the following list of errors to the WordPress support forums to get additional assistance.

I wonder what to do. Can I just delete wp comments and/ or wp options, or copy them from one of my other blogs? I have a xml backup, too, maybe just install a new blog and rename it then to …/ blog??
Many thanks for help.