Hi,
I have been trying to fix this issue for the last 10 days without any success. I have tried everything, search forums here and there.
I have upgraded from 5.2.1 to 5.5.1 and when I 'Repair Database' it shows the following message

/* Table : bugs */
/*COLUMNS*/
/*MISMATCH WITH DATABASE - f_code - ROW [name] => 'f_code' [type] => 'varchar' [len] => '255' */
/* VARDEF - f_code - ROW[name] => 'f_code' [vname] => 'LBL_F_CODE' [type] => 'VARCHAR' [comments] => '' [help] => '' [duplicate_merge] => 'disabled' [duplicate_merge_dom_value] => '0' [audited] => '0' [reportable] => '0' [dbType] => 'VARCHAR' */
/*MISMATCH WITH DATABASE - cc_code - ROW [name] => 'cc_code' [type] => 'varchar' [len] => '255' */
/* VARDEF - cc_code - ROW[name] => 'cc_code' [vname] => 'LBL_CC_CODE' [type] => 'VARCHAR' [comments] => '' [help] => '' [duplicate_merge] => 'disabled' [duplicate_merge_dom_value] => '0' [audited] => '0' [reportable] => '0' [dbType] => 'VARCHAR' */
/*MISMATCH WITH DATABASE - prodlineid - ROW [name] => 'prodlineid' [type] => 'varchar' [len] => '255' */
/* VARDEF - prodlineid - ROW[name] => 'prodlineid' [vname] => 'LBL_PRODLINEID' [type] => 'VARCHAR' [comments] => '' [help] => '' [duplicate_merge] => 'disabled' [duplicate_merge_dom_value] => '0' [audited] => '0' [reportable] => '0' [dbType] => 'VARCHAR' */
/*MISMATCH WITH DATABASE - pp_code - ROW [name] => 'pp_code' [type] => 'varchar' [len] => '255' */
/* VARDEF - pp_code - ROW[name] => 'pp_code' [vname] => 'LBL_PP_CODE' [type] => 'VARCHAR' [comments] => '' [help] => '' [duplicate_merge] => 'disabled' [duplicate_merge_dom_value] => '0' [audited] => '0' [reportable] => '0' [dbType] => 'VARCHAR' */
/*MISMATCH WITH DATABASE - pv_code - ROW [name] => 'pv_code' [type] => 'varchar' [len] => '255' */
/* VARDEF - pv_code - ROW[name] => 'pv_code' [vname] => 'LBL_PV_CODE' [type] => 'VARCHAR' [comments] => '' [help] => '' [duplicate_merge] => 'disabled' [duplicate_merge_dom_value] => '0' [audited] => '0' [reportable] => '0' [dbType] => 'VARCHAR' */
/* INDEXES */
/*MISSING INDEX IN DATABASE - bug_number -index ROW */
ALTER TABLE bugs modify column f_code NULL , modify column cc_code NULL , modify column prodlineid NULL , modify column pp_code NULL , modify column pv_code NULL , ADD INDEX bug_number (bug_number);

I have manually added varchar(255) in between the column name and NULL and execute it, it gives the message that database and vardefs are sync but when i do the repair again, it shows the same error message as mention above.
It seems that there might be some problem in my vardefs but which vardefs I have to edit I am not sure.