I solved my problem (with SDL) and it might work for your mozilla problem ie:
Reading Package Lists... Error!
E: There are two or more versions of the package 'SDL' insta which is a situation APT can't handle cleanly at the momentPlease do one of the following:
1) Keep at most one version of the package in the system; or2) If you do want to keep multiple versions of that package,uplicated in the documentation.
rpm -- erase --allmatches pkg name (in my case SDL)
If this breaks depends add --nodeps