Here we go. Put SD card in Win7 and Explorer offered to scan and fix, so I did:
Volume Serial Number is BA07‐5C55
Windows is verifying files and folders...
Unrecoverable error in folder \DCIM.
\TitaniumBackup\com.android.launcher‐42d0119466954cab95b941a0ef679cd9.apk.gz is cross‐linked on allocation unit
14355.
Cross link resolved by copying.
\clusb\Backup\companionlink2012‐11‐28.db is cross‐linked on allocation unit 14395.
Cross link resolved by copying.
\Android\data\com.cooliris.media\cache\local‐image‐thumbsindex is cross‐linked on allocation unit 14418.
Cross link resolved by copying.
\Android\data\com.cooliris.media\cache\local‐video‐thumbsindex is cross‐linked on allocation unit 14419.
Cross link resolved by copying.
\Android\data\com.cooliris.media\cache\picasa‐thumbsindex is cross‐linked on allocation unit 14420.
Cross link resolved by copying.
\Android\data\com.cooliris.media\cache\local‐meta‐cacheindex is cross‐linked on allocation unit 14422.
Cross link resolved by copying.
\Android\data\com.cooliris.media\cache\local‐image‐thumbschunk_0 is cross‐linked on allocation unit 14393.
Cross link resolved by copying.
File and folder verification is complete.
96 KB in 7 recovered files.
Windows has made corrections to the file system.
13,618,376 KB total disk space.
376 KB in 39 folders.
879,888 KB in 551 files.
12,738,104 KB are available.
8,192 bytes in each allocation unit.
1,702,297 total allocation units on disk.
1,592,263 allocation units available on disk.
Now all seems to be fine with other programs that were failing before to find the SD card. No reformat or reinstallation or nothing else required.